from my (1st rusto)experience if I could still see roller marks I just kept going until enough new paint blended right over them. In other words you probably need more coats.

The thing is I used to own a body shop and this stuff is all contrary to almost everything I learned while running my business. But with a little effort and trial and error it can look nice.
here's a truck I just did: new to this site so not sure how to post more pics. By the way I tried that wet sanding stuff between coats. No Way! way to much work. after 3rd coat I just laid em on real smooth with roller did about 8-9coats w/ no primer on a brown background. only reason I wet sanded after final coat was to bring out the shine in the very small metal flake I added to the last coat. after that I put a clear in an air can ad sprayed it on.