It's been a while (luckily), but I had a nasty experience where we were playing Bomb Rush and I rolled the bomb 4 or 5 times in a row on a 12 player server. In my opinion, if you roll the bomb, you should not be in the pool when the next bomb is assigned. Though it's statistically unlikely to happen often, it's not fair that one player rerolls the bomb repeatedly, while others can camp, safe and idle, on hard-to-reach areas (like trees in Seriouscraft).
Massive +1. No need to even explain it. Getting rerolled several times can just be a massive annoyance and sometimes cause your demise. Like Siddo said, make it so that the player who rolls it is Immune to rerolling it for 1 roll afterwards.