Ive been to all of Roberts premieres since I moved to California. Ive been to other movie premiers, Walk Of Fame ceremonies and many red carpet events. They are all different and the set ups can be tricky. You just have to feel it out and go with your gut on where you should be.
As for a time, it all depends on when they start setting up. People get there sometimes a couple hours before the red carpet arrivals begin or way earlier in the day.
We will all be there in matching distressed red Avengers shirts. There is about 12 of us so you cant miss us in the crowd if you go. We will be there with huge smiles representing DUF!!