How can I find the included single roles of a certain composite role?
Call transaction SUIM, access the menu Roles -> By Role Name, type the name of the composite role and execute. Now you can click on the button Included Single Roles (CTRL+SHIFT+F12).
If you want, you can do the opposite as well to find in which Composite roles, the single role selected is being used. Instead of typing the composite role name, you can type the single role name, execute and then Included in Composite Roles (SHIFT+F7) to achieve this.