Root App backup Question

[dport]

I rooted about two days ago. Once I install a custom rom, I am losing all of my free apps. When I go back to download them from the market again, some of them will not install. I have tried about 5 different roms and I have this problem with every one. of them. The main one I am talking about is Angry Birds (I have kids who love playing it). Should I unroot, save my apps with Astro File Manager and then root again? What do you guys think?