Work at Ascent of Olympus. The Greek heroes divines you can get for free through that have very high skills and can win rosettes. Their skill distribution changes daily so they can eventually win every rosette available and are almost guaranteed to win it as they usually have more skills than their normal horse competitors. Their skills also continually increase as the skills required to see rosette competitions increase. Normal horse skillers will eventually not have enough skills to see or win rosettes, you would need to buy or breed and train new normal horse skillers every few weeks to do it this way.