No, you cannot have multiple Battle.net accounts attached to the same Raider.IO account.
However, if you have multiple World of Warcraft accounts attached to the same Battle.net account, those accounts can all be attached to the same Raider.IO account.
Example: You have  Wow1, Wow2, Wow3, Wow4 accounts all on the same Battle.net account. The characters from all of those accounts will show up under your Raider.IO account.
Additionally, you can have characters from two different regions attached to the same Raider.IO account, but they must follow the rules above.