Bleys could go full Rogue if you ignore the thematic elements.
Classes of Amber
Julian: Ranger
Corwin: Fighter/Bard
Gerard: Monk/Cleric
Brand: Sorcerer/Warlock
Fiona: Wizard/Warlock (If she had any rogue levels, Brand would have been dead!)
Bleys: Rogue/Sorcerer
Caine: Loser
Benedict: Fighter, all Fighter, all the time, multiclassed into more Fighter, currently levelling up Fightest
Llwewlla: NPC
Flora: Rogue
Random: Bard
Merlin: Wizard