Similar to some posts above, I would also like to be an investigator. It seems like they are directly involved in the meat a potatoes of the trail. But I also think the IRB role is interesting as well. It sounds like the IRB role is a quality role to approve the protocol and ensure transparency with the participants about the trial details. The IRB ensures that the risks are reduced and are outweighed by potential benefits and reviewing research in order to advocate for the rights and safety of people who take part in research, both before the research starts and as it proceeds.