This question came up on the other forums and I was wondering if we could get an official answer of some sort. What does hitroll do? Does it affect combat skills? If so, could you give us an idea of which ones?

The last line of the help file should be fairly helpful with regards to the answer.

HITROLL DAMROLL 'HIT ROLL' 'DAM ROLL'
These affect your performance in combat. Hitroll affects how often you hit
your target. Damroll is added to your weapon's damage each time you strike
a target. In both cases, a higher number is better. These can be affected
for better or worse by strength, equipment, spells, and many other factors.

Hitroll does not affect the casting of spells.