Do they charge extra to reset the TPMS ?
If you have the dealer rotate the tires, my guess is they will have one service rate for that and include resetting the TPMS; I can't see them telling you that we had to rotate the tires and then charge you $10. for resetting as a result of that.
Now, if you take your Volt in to have that specifically done because you rotated your tires yourself, then they probably will charge you for that service unless out of the goodness of their heart, they donate their service time to you.
You can set it yourself by releasing tire valve air pressure and then adding pressure back in again but the process is tricky and has to be done in a logical sequence (refer to part of your owners manual for that procedure but the manual talks about using a 'wand'). There is other information on this forum for doing the 'air pressure' adjustment.
When I had my battery fix done, they HAD to reset my tires as part of the CSP.