It sounds like you have indexed shifters, in which case you need to understand a little more about what happens when you turn the barrel adjusters. You're not adjusting the cable tension (unless you're in the biggest cog already and you're tightening the RD against the limit screw), you're just adjusting the effective length of the cable and moving the RD slightly to one direction or the other. For indexed shifting to work properly the RD needs to be pretty much aligned with the cog when it's supposed to be in the gear. This is a rather finicky adjustment in practice, it takes patience and pro wrenches know not to do it with the customer standing right there as it can take time and profanity. If you're turned your adjusters two turns, they're already a mile off and you pretty much need to start over. The park and sheldon guides are good for this. Once you've done this you can see if you're still having a problem. Rough shifting can be a bad index adjustment, or it can also be cause by a worn cassette and chain. You want to replace both at once, as they wear in together.