On Tue, 2 Sep 2014 00:04:15 +0000 (UTC), "Danny D."
wrote:

Oren wrote, on Mon, 01 Sep 2014 14:20:35 -0700:

Notice the 2X10s have no knots. Nice wood.

What size are "normal" rafters?

Depends on what the truss engineer calls for from the blueprints, best
I can tell. Mine are 2X4, your's are 2X10. I've seen some 2X6 inch.

I'd image a lot goes into it the calculations, like roof loads, etc.
It's outside my pay grade