OptaPlanner VS JaCoP

However, if you need to solve constraints etc., see: https://www.optaplanner.org/

Try looking for something built around Optaplanner - basically taking the end game of rostering and working backwards.

OptaPlanner takes some of the items tracked in tool like Odoo and creates plans based on them. I.E. how do you manage shifts while juggling multiple constraints (Jerry can only work weekends, Jeff can only work afternoons, Jim can work weekends but only on double time, etc.)

There is a library out there called Optaplanner that is designed for optimization of NP complete problems. It is hard to tell if that is exactly what this is, but I think you should be able to use this regardless.

Just stumbled upon https://www.optaplanner.org. Looks very interesting but also really overkill.

OptaPlanner - a generic scheduler.

OptaPlanner

I've never used it but it sounds like OptaPlanner may be a scheduler in the same vein?

I used MiniZinc to model a scheduling problem for a customer which used constraints to block off already scheduled time, holiday time, non-work hours, etc. and it also had soft constraints for ensuring that blocks of time would be prioritized first to ensure that preferred representatives would get to a work with a given customer first based on previous relationship and skills. Once we translated the modelled constraints from MiniZinc to JaCoP in Java, the solution was able to generate hundreds of solutions per second. And note that it was able to do this minute level resolution such that no blocks of time were wasted because of scheduler limitations.