This is when the checklist can be your best friend. Run through it. It will probably suggest carburetor heat or alternate induction air to deal with the roughness. Other checklist items may also direct you to procedures that may smooth out the engine. Tell ATC or flight service of your problem.
Help is out there.
Do not hesitate to demand it. Keep your wits. This kind of ruins some of the fun of flying, but we're talking about emergency preparedness here, not poetic visions of the joy of flight. Targets and landings. The destination airport is drawing near.