Answer: I would strongly urge you to reconsider killing a street tree in the first place, and in the second place, frankly I would suspect it is just as illegal to herbicide one as it is to cut it down since the end result is the same. Instead, maybe you can improve the light conditions sufficiently to grow some of the mopre shade tolerant roses well.
To increase the light in your garden you might be able to limb the tree up, meaning strategically (and gradually)remove some of the lower branches that block the most light from reaching your garden. You might also consider increasing the light reflective surfaces within the garden by using a light colored paving material, a light colored mulch (eg gravel chips) and painting the walls of the building white.
You could also consider experimenting growing some of the more shade tolerant roses such as Zepherine Drouhin or Climbing New Dawn, Mme. Alfred Carriere, Fair Bianca, Abraham Darby, Sharifa Asma, Rose de Rescht, some among the polyanthas and hybrid musks, and many of the alba group such as Alba Maxima, Felicite Parmentier, and Konigen Von Danemark. Your local rose society and consulting rosarians should be able to help you identify roses that do especially well in your area and also tolerate some shade.
I hope this gives you some ideas, and good luck with your roses!
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