Fashion designer and Manhattan social fixture Rachel Roy is thinking of moving away from New York. Roy told Page Six last week that getting out of the city could be better for her daughters, Ava, 13, and Tallulah, 5. “I’ve really learned that raising two girls in a little concrete box is just not healthy,” she said at an M Missoni event at club Le Bain Thursday. “It’s kind of unfair actually.” Roy — who grew up in Northern California — says she takes the kids to the country, and recently hit Hawaii. “Honestly, it breaks my heart because I want to give them that more,” said Roy, who was married to financially embattled hip-hop impresario Damon Dash. “It’s a part of growing older — you get it, why people leave. I would love to run my company from a place that is actually good for them.”