No, Colin Powell does not play a huge role in the Clinton email scandal, except for the part with her trying to blame him for her using her own server. Colin Powell has basically said she's trying to blame him for the mess she's in and that she was using the her personal server before they talked. He has a very small role, not a significant one.
No, Colin Powell did not play a significant role int he Clinton e-mail scandal, Colin Powell advised Clinton to use a personal e-mail for unclassified messages. This advice given to Clinton by Powell does not seem to be anything but helpful. Colin Powell mentioned that he uses his personal AOL e-mail account for regular messages, which is the correct thing to do. There is no need to use highly secured professional business e-mail accounts for regular personal messages with friends.
No, there is no reason to believe that Colin Powell played a significant role in the Clinton email scandal. Even if Hilary Clinton told the FBI that Powell told her to use her private email for some things it probably was nothing that was scandalous. This is a sound bit that is meant to make the scandal even juicier.
No one knows exactly when Colin Powell told Clinton about using a private server, she may have been already using one by the time they talked. He made a mistake, she made a mistake, and now it is time to just let this rest. The FBI asked her about it, she told them, it's over.