If the roller table is not too loose you can make a paste with oil stone powder and oil . Smear it into the hole in the roller table and drive it onto the staff. Wash off the oil residue and the table whould be centered on the staff and tight.
Sometimes this caked on stuff comes loose, even Fried states that. I don't condone it but if you can't find a new roller or proper staff, you can try using removable loctite. If you mess around to much with the roller by punching it it can become off center and you can damage it providing a bigger problem. Removable loctite will be easily removable in the future by normal roller removing operations.
The problem with most attempts to attach a loose roller is that you cannot get it concentric with the staff and level. That is why the hair method is not good. If the roller does not rotate symmetricly, the safety dart will not work properly. It will not protect on one side and will retard the balance on the other side.
So using the abrasive or Loc-tite method at least gives you a shot at getting the roller centered and level. There is very little tolerance for the roller being off center or tilted. As others have said, these are methods of last resort or temporary repair.
I never install a staff until I have checked the roller and balance hole jewel fit. The roller should slide on the staff and stop about 1/3 the way from the roller seat, so that you only have to press it on the last third of the way with the staking set. If it sits much higher than that, you may split the roller when you drive it into its seat. If it the roller goes to the bottom without force, it will not hold. The hole jewels should sit on the pivots and tilt about 5 degrees.
If the staff is too fat at the roller seat or the pivots, you can turn it down. If it is too small in either location, you look for another staff.
There is a tendency among newer generation watch repairers to replace shellac with UV curing adhesive. They use this for jewel setting, crystal mounting and conceivable this could be used to hold on a loose roller. The only problem is that down the road a new watch repairer would not know this and could damage delicate parts trying to remove them in the normal way. This is why the removable loctite and grit/oil method is better because it allows for disassemble using traditional methods.
Don is 100 correct, that a roller should be trial fit before the staff is installed because at this time we can find another staff, roller,or turn the staff down.
Real watchmaking/repair is really an art form and takes a lifetime to develop the necessary feel/knack for how all these tiny parts go together.
True there are many beginners and hobbyists that can do cleanings and simple repairs but they have not yet gotten the real feel of these tiny parts fit together.