No, you can't flash cwm through rom manager on this phone. Even though rom manager has a version for the sidekick, it doesnt work right. backup/restore wont work and if you try to flash a rom you will probably brick your phone. others have heard the warning and have not heeded it, so whatever you do is on you. good luck.
Strictly for my ninjas
"And my time is a piece of wax, fallin' on a termite, that's chokin' on the splinters"
Devices: Huawei U8150 Ideos A.K.A T-Mobile Comet (sold)
Samsung SGH-T839 A.K.A T-Mobile Sidekick 4G (decomissioned)
ROM: GingerClone V2
Zeki 7" Jellybean tablet (tbd753b) current device