It depends on what you want to see. They are homophones. Rough is the stick from the deck. It also means rude, rough, ordinary, rustic, rough, coarse, vulgar, of poor quality. Vast, it refers to a very large, very extensive. It denotes a quantity, a dimension, a vastness to immensity. Vast, infinite, immeasurable.
The homophones, such as these, always have a different etymology. Vast drift of the vast medieval vulgar latin bastas bastare, carry load, is sufficient for this from the Greek bastadso, lift, carry, and hold. From here derive three interrelated meanings, the stick of the deck or stick ( in the medieval latin bastum, garrote ) rig carrying charge as the pack-saddle and also provided good animals, then thick, fat, and finally rude, ordinary, rough, rude, vulgar, apricot, plebeian, Lout, rude. Vasto is derived from the latin vast vast classic vastare, leave empty, let desert, devastate, obliterate and then leave a space and empty huge; Here the meaning of our language extensive, large, big, huge. Now Julio Cesar was talking about vastum mare ( 41 vast sea;.
