They’re kinda different
I have both, and use both equally.
Rollers are great for cadence and pedal technique, plus they are more engaging than a normal turbo.
I have the Cyleops Alu rollers with the added resistance unit, which does make them more flexible, and I can carry out interval sessions on them upto a fairly high intensity. I actually use them for standing drills, as they give a much more real feel, as the bike is moving as it would on the road, but it does take practice. You soon gain confidence, and can happily ride no handed, standing, one leg drills etc. Although I’m yet to get the one leg no handed thing down like that dude on You Tube!
Turbo’s are more flexible for specific training, ie interval, heart rate zones etc, as you can vary the resistance to a higher degree, and the bike being fixed allows you to push much harder without worrying about hurtling through the patio windows!
If I only had one item, it would be a turbo for its ability to do high intensity intervals, which given the boredom factor is the most common workout as it can give good results in a short workout time.