Times are getting tougher for those attempting to root Android
phones. While originally thinking that rooting the HTC Thunderbolt (Verizon's first LTE
smartphone) would be a snap, it didn't turn out that way: HTC locked it down with a signed kernel, signed recovery image and a signed bootloader.
It's reminiscent of what Motorola has been doing of late with its smartphones. That doesn't mean that the developers involved were unable to root the devices, but it does mean that, at least for now, there's no chance of custom ROMs.
On the other hand, if all you want is access to SetCPU and Titanium Backup, root is all that's required. Read through the long instructions at Android Police below, and remember that a) it will void your warranty, and b) you might brick your device.