I think the NFL likes their QBs to have hand sizes that measure at least 9 1/2" from tip of thumb to tip of pinky finger. I don't know that for certain, but I remember reading it in an older article. I don't know Romo's hand size measurement. I remember hearing someone on the radio say that Drew Brees had large hands, but I don't what his hands measured, either. The Eagles took Duante Culpepper off their draft boards when his hands measured smaller than they would have liked for a QB.
I found hand sizes for QBs from this past draft. Mark Sanchez has a 10 1/2". Matthew Stafford has a 10". Stephen McGee had a 9". Rudy Carpenter was listed with a 8 5/8".
http://BAN-INCOMING-IN-3-2-1/combine2009QB.php