"People often are in a rut at work. They come home, they're tired, they grab something because they have no time to think of what to cook."
Like many Kiwis, Roberts remembered eating lots of protein as a child.
"Yeah, life was all about protein, animal protein, not much fruit," she said. "Eggs, cheese and mutton."
Roberts' own move to veganism was caused by a severe eating disorder which controlled her life for nearly twenty years.
"I would become a recluse and I wouldn't want to go out," she said. "No-one could see it, no-one knew it was there.
"I'd come home from dropping the kids off at kindy and I'd start on a plate of Weet-Bix with cream, then chocolate slice. Then it would be lunch time and then I'd just keep grazing all day.
"Then the reality of what I had done would set in and then the depression and anxiety and shame and guilt… so then I would be bulimic [throw up] and I would be bulimic three times a day."
It wasn't until she was 44 that she discovered plant-based diets while recovering from a shoulder injury.
"I think knowledge is what empowers us," she said. "Why is an egg not good for us? Then the science comes in - well an egg was designed for a chicken. It has everything in there for a chicken to grow, not a human.
"And why would we drink another species milk after we're weaned? What other animal on the planet does that? So all these 'truths' started stacking up."
The welfare and treatment of animals was also a concern along with growing awareness that meat and dairy production is more intensive on the planet's resources.
Roberts has now been a full vegan for two years, and at 63 she feels better than when she was in her 40s.
"I guess the turning point for me was when I made a cabbage salad with some nuts and stuff in it and I saw my kids go 'ah this is nice'."
And the response from people who come to her cooking classes is also positive.
"After starting my new plant diet, I feel much better with my osteo-arthritis," Menata Haeta said.
"I just wanted to get back into being vegan again as it suited me and my daughter, so I'd like to try again, be motivated with Joesy," Helen Milner said.
"I mainly went vegan on compassionate grounds but the more I learnt about vegan over the years the more compelled I was to stay at it for health reasons," Annie Ranson said.
"But I'm not that competent a cook and coming here is a good way to learn to cook healthier food, especially when my son's involved."
Roberts said her actions will speak louder than words.
"It's like a religion, I learned just to keep my mouth shut. You don't preach, you just live it. If people want to change they can."
For more on Roberts' vegan classes join her group Joesy's Vegan Group in Ngāruawāhia
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