Crewing is entirely inflexible. You are allowed to request one flight per month,which may or may not be granted. The way schedules are individually
given appear to be arbitrary.
You can not plan on having the days off or the flights you need in order to commute back and forth to Europe. As BRU flights are popular because of the length of the layovers 48 hours + vs 14, pretty much everyone requests them, especially the Europeans.
Giving you a roster won't help. On average once the rosters are first published you will get 6-10 changes to it over the next month.
There is no bidding and no seniority sytem.
Sorry,but it sucks.