SRD rocs don't have a training entry, so maybe I wouldn't. But it's not a big deal to me; just remember that the DCs are harder for magical beasts.
Might as well. I was thinking of something like the following:
Training A Zakharan Common Roc
A Zakharan common roc can be trained to perform various tasks if they are tamed by raising them from the egg, but this is a very difficult endeavour. Raising a Zakharan common roc from the egg requires fifteen weeks of work and a DC 35 Handle Animal check.
The tamed Zakharan common roc can then be trained for the purposes of Combat Riding, Fighting, Hunting or Riding as per the Handle Animal skill, except the DCs are 10 higher than the defaults. For example, training a Zakharan common roc to bear a rider in combat requires six weeks of work and a DC 30 Handle Animal check. Riding a roc requires an exotic saddle. A roc can fight while carrying a rider, but the rider cannot also attack unless he or she succeeds on a Ride check.
Zakharan common roc eggs are worth 18000 gp apiece on the open market, while young are worth 36000 gp each. Professional trainers charge 2000 gp per week to rear or train a Zakharan common roc.
A combat-trained Zakharan common roc is worth at least 60000 gp (the combined cost of an egg and 21 weeks of rearing and training), a tame but untrained common roc costs a minimum of 48000 gp.
Carrying Capacity: A light load for a Zakharan common roc is up to 12800 pounds; a medium load, 12801-25600 pounds; and a heavy load, 25601-38800 pounds.
Regarding the crucial matter of cost. The original text says a common roc egg costs 2d6 times 100 gp, but that's obviously way too low going by the SRD examples:
Griffin (7HD, CR4) - eggs 3500 gp, young 7000gp, combat training 1500gp
Giant Eagle/Owl (4HD, CR3) - eggs 2500 gp, young 4000 gp, combat training 1000gp.
Hippogriff (3HD, CR2) - eggs 2000 gp, young 3000 gp, combat training 1000gp.
That looks like magical flying mounts cost 1000 gp/HD as young, and combat training costs 500 gp/CR.
For a Common Roc, that would translate as: eggs 9000gp, chicks 18000gp, combat training 5000 gp.
I fancied making the training costs 1000 gp/week, so a combat-trained Common Roc would cost 30000 gp (9k egg + 15k taming + 6k training).
That still felt too low, so I just doubled all the costs.
Does that feel right to you?
An Iron Golem costs 250% that much (150,000gp) for the same number of Hit Dice, but the golem has immunity to magic and a much better AC. Not to mention you don't have to feed and house a golem.