A groomer will trim him however you want, really. The most common thing we do with Rough Collies is just a bath and brush- brush out all the dead and loose hair/undercoat, remove any mats or tangles, get the dog clean and dry, then trim the hair between the toes. Of course nail trimming as well.
If you really want a groomer could trim the hair on his belly, britches, ruff, and feathers, but that's up to you. Groomers aren't mind readers, you need to tell us what you want!