The day before we met, she held an Organix 20th birthday bash at her home for the 45 employees and their families, while today marks the eighth anniversary of her joining the company.
Having started out as an account manager in 2004, she took over as md in 2008 when Lizzie Vann, the high-profile organic baby food trailblazer, sold the business to the Hero Group.
The cynic might wonder if the original aim to provide an organic, healthy and nutritious alternative to mass-produced baby food which helped Organix stand out from the crowd and find favour with parents had been watered down since it had been taken over by the international firm, which is owned by Dr Oetker.
Not a bit of it, insists Rosier.
"You do hear some horror stories when small businesses are acquired and sometimes in the selling process you think 'my god, you're going to gobble us up and spit us out', but for us it has worked fantastically well," she says.
"We get everything we want from them, but nothing more. Our organic, healthy, 'No Junk' ethos is the same today as it was when we started. It's printed in a booklet called The Spirit which we give to everyone who works with us, or for us, and it's only been changed once, to incorporate our new logo."
Not everything can remain the same at a company that now sells 100M products a year, and two years ago the business moved from its Christchurch "shack" "It was literally a shack", laughs Rosier. "It was sweltering in the summer and freezing in winter." to its current base.
But instead of focusing on the issues of ownership and location, Rosier points to what she claims were two more fundamental developments for the company's growth.
New markets
The first was the launch nine years ago of the Fingerfoods and Goodies ranges. These drinks and snacks, such as oat bars, crackers and rice cakes, marked its first foray into new markets and away from the jars of baby food that Vann had pioneered in 1992.
"Before Goodies and Fingerfoods we were fighting in the traditional baby foods market, and despite being successful, it was very competitive," Rosier concedes.
"We then hit on this idea of healthy Fingerfoods. Before this, people thought the only snack available for a baby or toddler was a rusk. They had no idea you could have the likes of rice cakes or cereal bars. This is when things really started to take off from a business point of view."
Rosier is proud of the company's first-to-market status with Fingerfoods and subsequent products, such as last year's Mighty Meals range. Here, the likes of chicken korma and pork meatballs are produced for one to three-year-olds to get them used to eating more solid foods.
Rosier says these innovations typify how Organix has success by giving parents something they didn't know they needed, but now wouldn't live without.
However, she is equally passionate about what she calls the second strand of the company's success, and that is its campaigns.
"Lizzie (Vann) was always so passionate and dedicated when it came to linking food and children's health, and did so much to promote it," she says.
She lists a range of achievements, such as working with the Soil Association to increase food standards in schools, providing a free food education programme for nurseries and contributing to an EU ban on certain colourings and flavourings in children's foods.
This campaigning zeal has now been enshrined in the Organix Foundation, a charitable organisation, which Vann still runs.
"The two strands complement each other really well," Rosier says. "We're really proud of our innovation, but equally so with our ethos."
With these factors helping to cement Organix's position as the prime producer of organic baby and children's foods, Rosier acknowledges it was no surprise that other companies saw the opportunities and entered the sector.
But while many mds would be wary of the competition and its impact on their businesses, Rosier views it as a badge of honour.
"If that hadn't happened, in many ways we'd have failed," she argues. "We wanted to create a world where healthy, nutritious food was available to everybody. This meant we had to set new standards, which everyone else then had to live up to.
"I'd be a bit disappointed if it was just Heinz and Cow&Gate in the market, because the new businesses are coming in and driving up standards too."
Noting that more than half of all baby food sold is now organic, she adds : "I'm not afraid of this competition, because it drives the standard higher and higher. The new players are also limiting exposure to pesticides and putting animal welfare at the top of the agenda, which we really welcome."
It is no surprise that competitors are entering the arena all the time, especially in the ready meals market which was worth £25.8M in 2011 and is growing by 23% year-on-year. This means Rosier is constantly on the lookout for new markets and even higher production standards, something that is easier said than done.
She says there are some "exciting developments" planned for next year, but unsurprisingly she is tight-lipped about the details.
Suppliers are paramount
With regard to production standards, she says the role played by the company's suppliers and manufacturers is of paramount importance.
Organix does not produce any of its products itself and works alongside"14 or 15 manufacturers" instead.
She says Organix insists, and always succeeds, in having full traceability for its raw materials. What can be more tricky, though, is finding the right manufacturers to work with.
"Sometimes we have to contact hundreds of people, to find one we can work with," she remarks. "The way we operate is to say 'here is a product we've made in our kitchen and these are the ingredients'. It can be a real challenge for manufacturers because they are used to using processing aides, which we don't allow.
"We know we are never going to find off-the-peg producers, so what we're really looking for is people with the tenacity and philosophy to partner with us to achieve our aims."
While it appears the ethos and innovation evident at Organix is paying dividends Rosier says it is mirroring the overall growth of 6.6% witnessed across the organic baby foods sector this is in stark contrast to the rest of the organic market which at best is stagnating, and at worst slumping.
Rosier says there are marketing and promotional issues at play here, especially in fresh produce, where a box of organic carrots "looks the same" as a box of conventional carrots.
Moreover, the situation is clouded by misguided press reports which are"obsessed" with the organic industry, she believes.
"It breaks your heart when you see some of the reports," she admits. "It's almost as though it is only the good stuff that some parts of the media are trying to critique. If colourings, flavourings, additives or some of the hydrogenated fats got that much coverage, people probably wouldn't be eating any of them.
"It's disappointing, but I guess we were used to it. Perhaps that should be our next campaign, finding out how to get people to look at the bad stuff instead."
With their campaigning track record, don't bet against it happening.
