I have a Bob Marshall and I am seriously considering selling it because it just loves to roll on me when I'm riding. It makes it extremely inconvenient. 

What kind of pads do you use with your BM to keep it from rolling?  

Sometimes the pad is too thick and that makes the saddle roll. What pad are you using?

On my older horses I use a Saddleright with a BOT liner and have no issues with rolling. On my 4yo I use a CSI with a BOT liner with the BM, but that's just because he needs to fill out a bit more. And when he does fill out I will go to a Saddleright and BOT with him also.

I use a Saddleright as well with a BOT liner. Also contemplating selling mine becuase it's making my guys back so sore

I love my treeless! I use a BOT liner with either a 5 star 1in pad or a 1/2 in cactus felt pad. Absolutely no rolling and I do use a shoulder relief cinch. 

I've sold a lot of the new style of treeless pads that 5 Star is making and people seem to be very happy with them.  We can still get the old style too since some do prefer those instead.  First pic is the rounded skirt new one, the 2nd pic is the XL with the square skirt.  They come with the Flex Fit front so no pressure on withers.

I currently use the reinsman pad for the treeless and have never had an issue with rolling on any horse. www.horsetackworld.com has a bunch of different ones in stock. She is the only place I know to get them

CSI

I used all of them and all thicknesses! LOL still rolled.

I ended up using just a liner and a navajo and I just had to tighten it SO tight for it not to roll. Im pretty sure this sored up my horse so I sold the Bob Marshall and went back to a treed saddle.

What kind of girth are you using?  I found I couldn't use mohair.  I have to use a neoprene.  I use either a professional's choice or an All American Tack neoprene girth.   They have to be pretty short girths, too.   And, no, I have never had one galled with them.  I swear by All American Tack's girth's.

For a pad, I use a 5 Star 7/8 inch pad or Diamond Wool pad. 

I use an impact gel. One of the older ones. The metal on the cinches seemed to dig in a bit much.

I use the 5 star 7/8 pad for the droped rigging, like the trail pad. And cinches I use the Professional Choice 32inch Neoprene or the shearling just depends on who I'm riding.

These are what I use on my BM, and my saddle does not roll. Nothing too fancy. 

I use csi. but there are those exceptions.... some BM saddles will roll on certain horses no matter what. My horses like the fleece liner csi pads. I know people that use just a good wool pad, or 5 star, saddleright, thinline etc. Its trial and error and rider preferance. But always make sure you have a short enough cinch. I went down from a 30 to a 26 or 28! I like the Prof choice shearling ones.

Currently I'm using a Thinline. In past years I have used PC HD pads and CE without issue. 

If I have a horse that the saddle wants to roll I use a roper girth. A good friend of mine has a mutton withered round back horse- she uses a 5 Star and a Sport Cincha (made by BM) and has no rolling issues. 

I use a 5 star- I believe the extreme racer with the wither relief. Love is! 

Is your cinch not fitting right? I had to switch mine when I went from a treed saddle to a treeless. I went with a fleece one.