Roundoff Correct Technique

Hello everyone,
I am currently working on all the different cartwheel variations, however I have been looking ahead at roundoffs and there is something about the correct technique that is not quite clear to me. Basically for what I've read the blocking action should occur from the shoulders and the arms must remain completely straight. However if I watch videos of basically every gymnast's floor exercise, all of them slightly bend their arms to get more power. Should this be avoided until working on very advanced skills or is it acceptable to bend the arms a little bit to get more power?

Avoid bending your arms, unless you need more power to "Punch up" off of the ground during a tumbling or vaulting pass. Always start learning the basic movement and then learn harder variations.

The round off is a required skill for most tumbling passes which requires a lot of motivation and drive to complete. It helps if you already have some experience with doing gymnastics before and know how to do a cartwheel.