lalapanzi
All depends on what size of airline you are working with numbers of crew and aircraft. Computer systems offer lots of advantages over and above the rostering element,e.g day to day crew tracking, ops control, statistical analysis and FTL records and more. On the other hand if you have only a couple of aircraft and limited number of crews there is still a place for a good manual roster and crew tracking.
I am sure the professional crewing bods will respond with a more in depth comment. But for what it's worth, there are a number of reliable and proven systems on the market and I would recommned you shop around and ask other airlines of a comparable size what they are doing.
But I can tell you that computer systems are not perfect and usually still require the skills of a good rosterer to set them up and 'fine tune' the output. But on thw whole few airlines of any size these days would be without.