A sedimentary rock made up of rounded fragments of other rocks is called a conglomerate.

Here's why:

* Rounded fragments: The rounded shape of the fragments indicates that they have been transported a significant distance, likely by water or wind.

* Other rocks: The fragments are derived from the breakdown of pre-existing rocks, making them "clastic" sedimentary rocks.

* Conglomerate: This specific type of clastic sedimentary rock is named for its characteristic rounded fragments.