Hi Ian
Part of the problem you'll face is that leisure (otium) was defined as one of the hallmarks of the aristocratic life; the labouring classes (from which most army recruits were drawn) were supposed to work - and did so much of the time! Balsdon's
Life and Leisure in the Early Roman Empire is getting rather dated these days, but provides some useful coverage on the concept of leisure as the Romans understood it. (*Edit - actually Toner's
Leisure and Ancient Rome is probably a better bet!)
Soldiers did have leisure time, of course, although the ways they used it tend to leave little to the archaeological or literary record. You might be interested in my
review of MacMullen's
Soldier and Civilian in the Later Roman Empire, which examines much of the non-martial side of the soldier's life. Davies's more recent
Service in the Roman Army covers, I think, similar ground - I haven't read it myself, but there's a
review here by Duncan Campbell which I can't seem to access at the moment...
You might like to look at the development of bathhouses in legion forts - as they grew bigger and more substantial over the centuries, they surely served as the foci of much off-duty time - not just bathing but general socialising, games and relaxation, in what for the average legionary (unaccustomed to the pleasures of metropolitan life) must have been very grand surroundings!
