[Roland]

Re-raising right away is fine, but slow playing is probably better. If you decide to slow play though, you should consider waiting till 6th street to raise (unless you think there’s some chance he’ll fold to a raise on 5th, but I can’t really see that).
Or, since you caught a scary-looking card on 4th, you could have raised right there (if you had slow played that is). Then you can raise again if you rag off and he leads again on 5th or maybe take it down right there if you catch another heart (hearts are somewhat dead, but he doesn’t have to be paying attention, does he).