I am not sure if its a good idea to walk in upwards rather than the normal downwards.
because if u think of it u will be walking twice the same space in order to go up and down
i know from ''forgoten'' clients of mine that there are tavernas to eat and places to sleep, but i have no idea about names or prices.
personally i wouldnt do it that way, and i would have tried the normal excursion so as i would have walked only one way and see all of samaria rather twice and see half.
another possible idea is to start organised trip but four you to have your accommodation booked for a night or so in roumeli. that way you can have a base in chania or somewhere else, do the walking, spend the night in roumeli and the following day go back to your base. my idea might sound stupid as you will be paying for accommodation without using in the ''base'' but still you will be able to see all of samaria and spend the night in roumeli