I suppose you mean if it is possible to play RoL over the internet where the 2 computers are using the same router.

You might be able to by using a program like Hamachi or GameRanger.

Note that you might have to manually make sure all programs have free access to the internet, both on the Router and on both computers.

It is not possible to change the ports RoL is using, I also don't believe that would make a difference as all that does is changing the access port on the same IP adress (it's like using another door than usual when entering or exiting a building).