I also had an incredibly loud, irritating creaking sound on my road bike. I resolved it in two steps. First I found that my skewer wasn't very tight. After adjusting it to clamp harder, the noise was reduced a lot. Next, I applied a thin layer of Copper Slip between the frame and the hub. After that the bike was silent. Putting your bike on a trainer meant that you had to fiddle with the skewer, so maybe the above applies to your problem.