I have a roof rack and have had both kind of trays... the one where you never have to take the front wheel off and the fork mounted one. I hated the one that you did not have to remove the front wheel. I think it was called the Raptor. I never felt like my bike was secure. The fork mounted method works MUCH better. Yes, bugs. Yuck! I like the saran wrap idea -- may try that. Yes, MPG decrease.

My next vehicle will have a trailer hitch and hitch-mounted rack. Easier to get to, no drag in the wind, fewer bugs to clean off.