Hi Jared,
Unfortunately there is currently no way to specify that a resident would like a certain rotation on a certain block. Making Annual Rotations Schedules (aka "Master Schedules") in the MedRez.net Scheduling Tool is a manual process at this time (the Randomizer is for Call / Shifts schedules).
The easiest way to deal with this situation is to give residents their preferred rotations at the beginning of the schedule-making process, then fill in the remaining blanks.
You can also set rotations to allow vacations or not. This allows residents to request a vacation-friendly block by requesting a vacation during the block (they can later change their actual vacation request if necessary).
I hope that helps,
Regards,
Olivier Forget
Owner and Developer
MedRez.net Scheduling Tool