I know many of you asked me on how to root AT&T Galaxy S2 Skyrocket SGH-i727 but I don’t have that model.
BUT, the steps to rooting is nearly identical to T-Mobile Galaxy S2 SGH-T989 but you use a different recovery.
To root AT&T Galaxy S2 Skyrocket SGH-i727, simply follow the latest T-Mobile Galaxy S2 root method BUT for Step 6, instead of using “recovery-cmw-hercules.tar”, use the file “SkyrocketCWM126.96.36.199.tar”!
I don’t support the SGH-i727 on this site but if most of the instructions are nearly identical to T-Mobile S2 so you can refer to the T-Mobile S2 FAQ.
For custom ROMs, check out the Skyrocket thread on XDA, most of them should be good, I would try BeanStalk or Carbon ROM.