Can I freeze leftover risotto (already has cheese, peas and mushrooms in it)?

Rice doesn't freeze well period. Freezing breaks down the structure of the rice, leaving it grainy with a poor mouth feel. Can you? Yes. Should you? No.

I do !
I form patties like burgers, freeze, then thaw and pan fry. Crispy on the outside and warm and mushy on the inside.

Risotto should be made and eaten fresh. Why risk eating something not quite right, eat it fresh and then fry the leftovers in patties the next day.

i always make a big batch of risotto and freeze it in pillows. Let it defrost at room temp and then nuke it (not on the highest or the butter will separate out and it will be greasy) and yes, my risotto always has something in it- shiitakes, chanterelles...)

My experience with leftover risotto has been somewhat gummy. I don't THINK that freezing would hurt it - might need a bit of loosening when you re-heat it (with some broth or water) - but if it's freeze it or waste it, I'd say go ahead and give it a try! Then let us know how it is afterwards!!!