In attempting to advise people on how to condition a roping horse, I feel that there is no simple answer and there are a lot of considerations. Factors such as age, level of training and existing musculoskeletal problems all should be considered in developing an individual plan.
I believe that when you're bringing a young horse along, the common-sense approach on how to get the most done training the horse satisfies the conditioning requirements. The horse's mental state and need for slow, repetitive activities will automatically make the horse physically fit. As an example, I believe if you pay attention, the young horse will tell you when he's ready to start making some training runs at each ride. You shouldn't start running any cattle until the horse lopes around with comfortable control and gets relaxed. Depending on the horse, that may take 15 minutes or an hour.
Older horses also have varying needs of just riding depending on their personality. If you're roping on the "average" horse a few days a week and you warm him up properly and make eight or 10 runs, I think his fitness will be fine. If you have a solid, old horse that works fine without regular practice sessions, I believe you should still exercise him regularly with jogging and loping. Muscle tone and fitness, with a sound mental state, are the best preventatives against limb trauma that may lead to unsoundness that you can invest in.
Other factors that impact the conditioning or general fitness of a roping horse are diet and housing. It's easier to maintain the fitness level of horses maintained on a mainly hay or pellet diet that live in an open walk-around area than horses that are grained heavily and live in a stall. You will also have fewer stable vices (such as "cribbing" or "weaving") and metabolic muscle disorders such as
"tying up" syndrome. The weather can also play a role. When it's colder, it typically takes longer to get a horse to the point where he's ready to pay attention than when it's warm.
One last comment: Never do 50-yard "wind sprints" to get your horse fit. That activity poses unnecessary risks for potential trauma, and it just makes one crazy