I was under the impression that people can 'bid' for 'types' of rosters e.g. 'Max time away', 'Min. time away'
It's not that simple. Each month you're presented with a large number of pre-written lines of work /rosters. You then bid to try get one of these and seniority rules. Some of the bidding programs that allow you to finesse your bid do allow you to select parameters that can bias your bid towards criteria such as minimum reports, minimum time away, etc, but if you are junior you're only going to get to bid from the lines of work the senior guys and girls don't want.....draw your own conclusions as to what is on the lines and what days of the week you're likely to be at work.
If you don't get a "line" you get a roster (blindline) made up of the work that, guess what, in the main the senior guys don't want.
(Edited because the original was done on a connection with limited access and didn't allow any tidying - hope it's a bit clearer now))