How wide of tires can I run on a Victory Vision road bicycle?
What tire width can be safely used it mostly determined by the width between the bead seats in the rim.  This can be measured and is often listed in the specifications for your rims.  

Then I use Sheldon's Tire sizing chart to figure out which tires will work.  That link is to a long article on tire sizes, the rim vs tire width chart is red &amp; green and is near the bottom of the article

Edit

Near the top of the linked article is a nice picture showing where to measure inner rim width.  This determines if the tire will stay put on the rim.  Both too wide a tire on too narrow of a rim and too narrow of a tire on too wide of a rime will not seat correctly.

As freiheit points out you also need to check for clearance issues around chainstays, seatstays brakes etc.