If it hurts too much with your current roller, get something softer.  I am a big fan of the yoga tune up balls, myself.  The two balls together are just the right size and squish to keep the pain manageable.  Move to harder rolling devices after you can handle the soft ones.

You can use the balls to get the front of the hip just under the bone as well.  For the rest of the psoas, see the gut smashing mob.  If you don’t have a soft ball kicking around the house, I have used a cushion on top of a soft foam roller or just a rolled up cushion or ball of towels.  It’s better than nothing.
http://www.mobilitywod.com/2012/06/jill-miller-smashes-your-guts-and-psoas-and-tacked-down-viscera-and-matted-down-abdominals-part-2/