Hey I also used to live with flatmates in my first year at uni. They were mostly girls (I'm M) lol so a little bit different, at the time my stutter wasn't too bad. My advice would be to occasionally join them in the kitchen, you don't necessarily need to talk loads, maybe acknowledge them and ask about their day. It's also important though to give yourself space so only do this occasionally, you should feel comfortable in your accommodation. There were only two stoves in my kitchen in a flat of 8, you could maybe schedule together certain times when you want to cook, that way you can cook without feeling the pressure of having to talk too. Overtime you might feel more comfortable talking with them, I'm sure they like you and won't mind if you stutter.