Repotting Bird of Paradise

I've acquired two birds of paradise plants ! They're not in the best of condition leaning and climbing out out of their pots.

I've taken them out of their pots removed all the rotten roots and bricks then put them back in with new compost vermiculite sand and bonemeal, the problem is they are still sitting quite proud with old roots showing,I can't put them in any deeper and still have compost below the roots.

i haveread they like to have roots at the top of the pot but how much is too much ? without blowingthe budget I don't have even bigger pots to put them in. 

Any advice ?