Yes it's best to cover pork roast when you're cooking pork in the oven.
You don't have to cover pork to roast it in the oven but by covering the pork in the oven it helps to retain the juices of the pork.
Keeping the juices in the pork helps prevent the pork from drying out which makes the pork more juice and retain it's flavor.
I always cover pork with some aluminum foil before cooking it in the oven and it comes out better than not covering the pork.
But you can cook pork with or without covering it but covering the pork when cooking it makes it much better.