okay first of all what area of canada do u live in? secondly where did u get your information that there is nothing that u can do about it.
this persons trees are a nuisance to u and your elderly neighbour for the use and enjoyment of your property for one thing and for another thing the branches coming across your fence are also considered a private nuisance.
therefore look into the torte law in canada called private nuisance law.
http://www.bcwatersheds.org/issues/w...wlp/q3-1.shtml
http://www.duhaime.org/LegalResource...-Nuisance.aspx

there are two links that should be able to help u. i would be sure to take pics of those tree roots, of the trees sitting at the top of your house, of where it is near your window etc. get pics also of your neighbours and whats going on there with the trees and also have your neighbour back u up in court if u can cause the more grease to the wheel the better the action on things.
your neighbour for one thing is enroaching on your land and here in canada that isnt legal no matter what anyone tells u your neighbour is responsible for what his trees are doing and is held legally responsible for it.
so good luck and let us know how it goes . cyaaaaa, sockiescat .