The xda developers has rooted htc EVO 4G Froyo version successfully.The rooting method for the EVO 4G is close to the same as the Droid 2.Here i’m giving you the complete step by step guideline.
Disclaimer: Please do it with your own risk.We are not responsible for any damage.
The steps are posted here.
Wow way to find this about 5 months too late! That thread is outdated and it’s not a successful method anymore