Generally speaking, Roland’s turret doesn’t really do that much damage come end game (early game is a different story). So I would remove points from Sentry, Stockpile, and Barrage.
Max out Impact, it’s a better skill that it would appear because the effect stacks multiplicatively with other damage buffs Roland can get (it’s bullet damage, whereas the other effects would be weapon damage, a different variable, and hence they stack multiplicatively).
For the Support tree, I recommend Defense (better than Stockpile imo) into Quick Charge (amazing skill), you can opt for Grenadier if you find yourself liking Grenades too (another good skill).
You will end up with 54 skill points (53 after specing your action skill) once you reach the level cap of 58. However if you have the 3rd DLC, Secret Armory of General Knoxx, you will have 11 more levels and hence 11 more skillpoints, furthermore, both DLC2 and DLC4, Mad Moxxi’s Underdome and Claptrap’s Robot Revolution, there is a bonus skillpoint available from each of the two playthrough from each of them, for up to 4 more. This gives a total of 69 skillpoints (68 after speccing action skill).
I typically use http://87bazillion.com/skillcalculator/ to display skill trees. Here is what I am recommending for you:
This is only up to level 40, after that, I would probably go for Grit into Stat (another amazing skill) in the Medic tree.
Here is what I often run for endgame on Roland: http://talent.87bazillion.com/soldier.php?505555050505535050055
Works great with all of his offensive coms; Commando, Heavy Gunner, and Rifleman