I have a commissioner wanting to update our road use agreement for heavy trucks.
It looks fine; however, he wants to leave the County Judge's signature off?
I have not seen such and do not want to do this.
Do I need to look at this differently?

In my opinion, it depends. If the Commissioners Court as a body, agrees to an updated road use policy, a sign off form and includes in the policy that the individual commissioner may handle the paperwork as long as there are no exemptions or changes to the policy, I don't see the issue.

If the commissioner has the authority over the roads in his precinct as most of them do - properly drafted, this would seem reasonable to me.