Make sure that you are using the right size pan. If you do not have a larger size pan then use 2 smaller ones. Ultimately you want the dough to have enough space to spread out wider and stick to each other. If there is no space then the dough would rise in the centre and create that bulge-like a pyramid. 2. Overproofing is also the culprit. For the second rise make sure that rather than going by the time you check your dough. You want the rolls to stick to each other once done put it for baking, if allowed too long to prove then again it would rise from the centre.