Can you stand on these to simulate...
Can you stand on these to simulate climbing?
Not very easily, but with practice it is possible. It takes a tremendous amount of balance/skill to stand up on rollers. Rollers require an even amount of pressure through the pedal stroke which builds good technique. Stomping on the pedals will force the bike to wash out from underneath you. A standard trainer might be a better route if you plan on doing extended standing right away.