The job changed quite a bit over the years as I moved up and as the terms of reference of what LegOs did and had to do.
In my early years as a major I was a jack of all trades doing all of the above and much more. One of my biggest roles then was "legal advice by walking around" which essentially was visiting the district's units during their parade nights and exercises and having coffee with folks. It's surprising how much you can find out about the issues a unit is having by having a friendly cup of coffee with them. I also did a fair bit of prosecuting and defence work in those days. (This was before DMP and DDCS when we prosecuted within our own region and would be called on as defence counsel in other regions). A ton of lecturing on Ops Law (primarily LOAC) and Mil Justice.
As lieutenant colonel DAJAG the job was mainly supervising all the ResF LegOs in MilAreaPrairie, dealing with the district commanders and CWO on broad legal issues and working on appellate cases before the CMAC. That later switched to a role as a DLaw/SP with DLawT to do training which turned out to be a bust (funding issues for exercises) so I turned my attention to creating policy documents for ResF LegO governance and a further ton of lecturing on Ops Law.
My last job as DJAG/Res was a the CAF's senior ResF legal advisor where I was concerned with overall governance of all ResF LegOs (but not command as that remained within the various directorates), advising CRes and Cadets and Council; providing legal advice on various ResF centric projects and participating in international ResF agencies (a lot of swanning around on that but very busy).
Long story short. The job a ResF LegO does is very much dependant on what they are willing to do and what their AJAG or Director assigns them to do. Some stay connected primarily to their ResF brigades and provide the bulk of the legal services to them while other who have special talents are much more used across the board. Each of an AJAG office, DMP and DDCS is in fact a total force organization which is commanded by a RegF LegO with a ResF deputy and a variety of RegF and ResF LegOs with varying talents. How each operates is very much personality and ability driven.
One point on contracts. In my day there wasn't much contract work for AJAGs (and none for DMP or DDCS that I know of). Much of that is specialized work that's more in the purview of DND&CF LA (and prior to DND&CF LA there was a JAG directorate that did most of that). There was some minor claims work decentralized to AJAGs but contracting isn't really part of what ResF LegOs get involved in even though some of them were experts at it in their private practice.