User blog comment:Gilgamesh79/Demonic Energy and Magical Energy/@comment-82.178.102.63-20170829160229/@comment-1359322-20170831085243

"“Fuhahaha! Good! That flow of demonic power! The demonic-power I can feel right now is that of an ultimate-class devil. A little bit more then you would reach that of a Maou, Rias Gremory! Looks like you have a talent equal to that of your brother’s!”"

- Volume 3

In Volume 3, Kokabiel noted how Rias' Demonic Power reach Ultimate-class with Ise's [Transfer]. It means Rias didn't have Ultimate-class Devil power but now in Volume 22, she became capable enough to beat an Ultimate-class Devil on her own.

Also even if Sairaorg can use Demonic Powers he has another issue that would prevent him.

"Sairaorg-san continues to talk to Rossweisse-san who is in thought about it.

[It may sound weird. For a Devil that was the source of magic to learn magic. But it’s also true that there are Devils that are bad at using demonic-powers. There are also children who can’t use demonic-power like myself. That’s why I want to teach the foundation of magic to those children. Even if they can’t use demonic-power, there is a chance that they can use magic. Even if they couldn’t acquire magic, their knowledge behind it will become a powerful weapon to them. I don’t care after how many years it is. Will you take the role of a teacher?]"

- Volume 17

Sairaorg has limited Demonic Powers but no access to it. Ise has access to it as seen with his Dragon Shot, Dress Break and Pailingual. There's a difference between them.