I don`t use any texture rollers but some hand made tools
look at my work here and if you like the bark then I can tell you how to do it
Easiest way to get a bark texture without stamps or rollers is take tinfoil, crumple it up, open it and press into your mix. If u want to get under peeling of the bark take a roofing nail and drag down. Use the head of the nail. This will tear the mix and give a natural look to the bark. Then fine tune with a dentist pic. I've used this technique on a lot of free hand bark/tree work. I will post some pics to see if this is the look you are going for.
The nail technique is a nice one but never drag down do it upward
i will send you some pics and short video to explain a bit