1.One of the option is using css to set width of the RadMenu item. In this case you should use long menu name, so it would format rows.
2. Second option is using images for the menu items.
3. Third option is using RadMenuTemplate
the Telerik team
Do you want to have your say in the Sitefinity development roadmap? Do you want to know when a feature you requested is added or when a bug fixed? Explore the Telerik Public Issue Tracking
system and vote to affect the priority of the items