You don't mention which particular Roland Blues Cube amp you have and I'm first hand unfamiliar with the amp. However a quick bo peep at their website illustrates some of the higher end models already have a ton of inherent selectable effects and voicing features. 

So given your genre predilection, be pretty hard for you to go wrong starting with a BOSS BD-2 Blues Driver pedal. Perfect if yours is the few frills portable KISS single channel version.