I'm not sure I'd say comfortable. Three 10'x10' bedrooms would leave you with 600 sqft remaining to play with, and that's not a lot of room for two bathrooms and a decent-sized living space and kitchen, not to mention closets and any kind of storage space (which the need for increases with the number of people who live there).

My 1BR is around 900 sq ft, and I'm having trouble envisioning how you'd carve two more bedrooms out of it and still have a nice space. One more bedroom, sure, but two more feels like it would be a stretch.