Yep, there's a reason why roses are sold as grafted plants, Keith. The rootstocks are chosen for various good traits like hardiness and pest/disease resistance, then the varieties with great flower qualities are grafted on those stout rootstocks.
Your die-offs were very likely disease, but they'd be diseases that grafted roses might be resistant to. If you want to 'grow your own' roses, you'd be best to start with cuttings from what are known as 'own root' roses like the Knock-out series of landscape roses.
