You can use roles in a few ways. You can use them as placeholders for activity assignments you know you need, but don't know the actual resource (named or otherwise). Some organizations use the role as the resource name and go that route. Seems like you're using 6, so roles usually can just be added to your activities as you are building your schedule and you can do your planning/budgeting that way if the roles have costs assigned to them. This way, you can get a cost estimate even if you do not know the named resources.
As for EV, this is a topic we could talk about all day here. What exactly is the end goal of what you are measuring? I imagine cost and schedule, but do you know what EV attributes you are looking to measure? All of them. There are plenty of books that are out there. A partner has a pdf out there and there are tons of videos and material out there on this topic.