Its time for a new front tire on my Rocker C. Factory tire size is 90/90-19 my question is will a 100/90-19 work without any issues. thanks for any help.

 

Yes, it will work fine.
I'm using the Pirelli Sport Demon 100/90. Highly rated on sport bikes, sticks well, doesn't wear too well. The Avon Roadrider on my other bike seems to wear much better.
Hard to compare handling and traction between the two without throwing them around on a track, which I haven't done. Also, it's pretty hard to really test the handling of tires on a Harley, since we run out of cornering clearance before most tires are pushing their limit anyway.