I can't find the "Rotational Multibody Interface" block in the simscape library but I have installed the most recent version of Simscape and Simscape Multibody
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Steve Miller on 26 Nov 2022
I promise you, they are there!
Here is where you can find them in the library browser. You can also use quick insert to put them in the diagram by just clicking on an empty spot in the diagram and typing "multibody" and it will appear in the list.