My recommendation would be to have your labs checked about 3 months post-op to see if this is something you actually need. Most of us (not all!) don't need B vitamins beyond what's in our multi, as B absorption, especially B12, is generally a problem with gastric bypass rather than DS. But there are exceptions, so all of us need to follow our labs and adjust when needed.
Just this past year, at 12 years post-op, my B6 level dropped from mid-range to low normal, so I've started taking B6. I have no idea why this happened. It's still the only B vitamin I need to supplement. Others here do need B12. You won't know til you get there.