Thanks a lot for you comments guys. Here is an update on my case:
I coated some of the roots with varnish (it's semi-gloss, didn't have any matte) and they look good. I'm going to put them in a bucket and see what happens.
On Saturday I went to a small river close to the city, collected a LOT of driftwood and took them home. I found different types of wood, some still had the bark, some didn't, a few don't float but most of them still do, some are roots, some are branches; but all of them where in the water when I picked them up. I really enjoyed the experience.
Once I got them home I laid them on the floor to select the pieces that would fit best my aquarium. I forgot to mention this, but I'm building a paludarium as well as a normal aquarium, so i need some wood for each. I ended up selecting a beautiful piece of root for the aquarium just for it's great looks and because it fits perfectly in the tank. The downsides of this one is that it still has all of the bark and it's very light, so it floats. It even seems like it wasn't in the water, maybe it only had a few days there. Anyway, I cut it to give it shape, cleaned it a little bit with a brush, filled the tank with water (it's brand new, so I still don't have anything in it) and a little bleach, then I submerged it with the help of some weights. I did this last night and this morning the water was still very clear. I'm going to wait and see what happens. I hope in a few days I can remove the bark and that it starts to sink on itself. I really want to use this piece. I might be able to get a big pot to boil it to speed up the process.
For my paludarium I selected a branch with great ramifications. This one has almost no bark left, it weighs a little more but doesn’t sink. I put it in the tank with the other one. I’m not sure about using it because I’m not really convinced it’s what I have in mind for my layout, but I’m going to treat it anyway just in case.
I might go to the LFS (see, I’m learning already

) to see if they have a piece of driftwood I really like, and maybe I’ll return to the river next Saturday to look for some more wood.
What do you guys think about the piece for my aquarium, do you think I can make it work? If it helps I could upload some pictures.
Thanks again.