Okay...thank you all...
I'm not an expert and I said that I will use a 9sp cassette because I think that a mtb 9sp RD will only work with a 9sp cassette...but...as "well biked" said this configuration on my new bike will work:

Shifters: Shimano 105 5703 10sp-compatible
Cassette: Shimano Deore XT M771-10 (10sp cassette 11-32)
Rear derailleur: Shimano Deore XT M770 (9sp-compatible)

right?!

for the front the solution can be mounting the 105 triple 50/39/30...and everything will be okay...and it can be good to me...
but I'm curious...suppose I would like to mount more lower gears because I will travel with bags on hilly roads...

I'm wondering about if you can help me in founding a 48/36/26 crankset that operate with a 105 fd...or maybe a fd that will work with 105 levers and a 48/36/26...
any solution of same-quality component can be good but I would like to maintain the 105 sti levers...