What do you call a round bread roll?

[Pearl]

A bun is cakelike and square.. Hot cross buns have a cross on each one in white icing and are usually available around Easter.

Yes there are hot cross buns, not all have the cross in icing but hot cross buns are different than bread buns, hot cross buns are sweet with dried fruit and usually cinnamon but bread buns are plain and can be used with fillings like sandwiches.