Yes on both counts, however, though it's common practice, it is not necessary to prune back crapemyrtles if they are planted where they have the room to grow to their desired size and form. (There are many, many varieties of all sizes and colors.)

There is a tab you can press on our Rose page about pruning roses here: https://extension.umd.edu/resource/rose-identify-and-manage-problems/arec.umd.edu/resource/rose-identify-and-manage-problems
and be aware, there is a new pest insect- Crapemyrtle Bark Scale to keep an eye out for: 
https://extension.umd.edu/resource/crapemyrtle-bark-scale-new-problem-home-landscapes/


Christine