The defined homepage of the first matching user role will be presented.
Isn't the start page set to a project security role? If so why would you give a user different project security roles? In my oppinion a user should have 1 project role that consists of different module roles.
In addition to Johan's correct answer for the first part of your question, an answer for the second part of your question (organize the order of the alternative home pages) is:
Yes you can! Use drag and drop to re-order the alternative home page items.