I rooted my Evo and was running the stock ROM with the udated radio, and I was having problems with my 4G service while I was at my mother-in-law's house. I was looking at xda-developers.com's forums, and flipz had released a 4G patch along with his Fresh ROM. Figuring that things couldn't get any worse, I flashed it and my 4G started working. So, if you're having 4G problems and are rooted, then you might give his patch a try. It worked for me, and it most likely will work for you.
http://link.geekfor.me/fresh4gpatch
http://link.geekfor.me/fresh4gpatch