once a day is good. It's like having deep tissue massage, doing it too often can get painful. So that being said, if the intensity of sensation is getting worse each time you get on the roller, you should decrease frequency. If it feels good every time, you can do it more often if you want to. But start with 1 time per day and go from there. It's good to take a hot shower and stretch afterwards too.
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2007 Look Dura Ace
2010 Custom Tonic cross with discs, SRAM
2012 Moots YBB 2 x 10 Shimano XTR
2014 Soma B-Side SS