The Bolshoi never announces casting when tickets go on sale online. If you are planning a trip, but you want to see a particular dancer in a particular role, it is best to buy a ticket for each performance. You can return the tickets for a full refund online as long as you do so 10 days before the performance. By then the Bolshoi will have listed casting on his website. You can return the tickets for the dancers you don’t want to see and keep the ticket for the dancers you do want to see. However, if it is a premiere of a new work, they may not list casting until a few days before the performance. In that instance, best to buy a ticket only for the night you will be in Moscow. The tickets for every performance sell out months before. In contrast, the Maryinsky lists the casting for the tickets that are on sale. They cost a lot less than the Bolshoi even though the theater has fewer seats. They also do not sell out as quickly. However it is a good idea to purchase the tickets as soon as they go on sale for the best seats. I don’t know what their return policy is