Just recently purchased an R15 rucksack with the ability to fit the hydration pack. I bought the R15 because it's designed to work with their waist-packs, it's higher at the base to accommodate them.
I have the hydration pack and it was very good across Europe. It has Velcro on both shoulder straps so you can have the tube on the left or right side. The mouth piece is also superior to the Camelbak in that it has a sliding feature. You pull it out with your teeth and then suck... (sounds weird I know)
Another good feature is the way it fits snug to the body and has minimal straps to flap around in the wind.
I considered the enduro waist pack which can also take the tool roll. When I filled the tool roll up and realised how heavy it was I thought I wouldn't be too keen to have all that weight slung around my waist which would be in addition to my beer belly