It's kinda hard to help when there is no map available for us to look at.
But by the sound of it, you should fly the 312 radial FROM La Belle. so whatever heading you're flying prior to La Belle, you should track the 312 radial from La Belle VOR
ROGAN is a "named waypoint" or a CNF, Computer Navigation Fix, commonly these are known as intersection. They are easily recognized by their 5-letter name.
If you study ROGAN it may very well be a position where two or more airways crosses eachother.
Another way to determine where the ROGAN waypoint is to compare VOR radials and distances in the surrounding area...I would not be surprised if that's the case here, you have the chart infront of you so it should not be a problem, and since ROGAN is a part of the arrival I bet the radial and distance from La Belle is marked on the map.
These ROGAN-type waypoints are no radio navaids, so they have no frequency at all

They are references for aircrafts using navigation systems with a navdata-base.
The assigned approaches and arrival routes depends on where you're coming from and which runway that is currently active, don't know what the case is with Tampa Intl, sorry