well... you want to have a roll around and see what you find.
in my experience pain around a joint gets me searching the muscles either side. so in this case the muscles in your lower arm and the muscles in your upper arm. i like to try and rest my head on the part being rolled for additional pressure when i do my arms. start by trying to roll along the length of the muscle feeling out general tenderness.
do this for a couple minutes to promote blood flow. after some time you might start to get the impression of more focal points of tenderness / tightness. then spend some time on those areas. sometimes a bit of cross-friction wiggling across the muscle fibers alternated with elongation rolling seems to help. sometimes fairly firm pressure on a particular point for about 60 seconds helps it to relax. the idea is to try and get tight muscles to relax. also to promote bloodflow which promotes healing.
triceps are tricky. i have most success with lying on my stomach and holding my arm out over my head. rest my head on my arm. do your armpit, too, for good measure and round the back of your shoulder joint.