Mine had all that 'scaly' rust, caused by moisture trapped between the headliner and roof.
It's good that you were afraid to blast there. My media blasting shop refused to blast it, and my body/paint guy agreed with the decision. Apparently, those roof panels are susceptible to stretching slightly, which can cause your paint to look wavy later. I went with their recommendation to lightly wire brush it, and seal with POR.
-Tom