I too think you shouldn't soak your veal in lemon juice as it would pre-cook the meat, which cannot be recommended in this case.
If you're not sure about the quality of your meat, have it cut very thinly with a meat slicer, like ham. This is a trick I often use when I have only few time left to cook my Involtini. I cover these thin veal slices with thin slices of prosciutto, put cheese and sage in the middle, roll up the involtini, cut them in 2 inch pieces and fix each piece with a toothpick (or skewer 4-5 pieces together). Then I proceed as usual. This way, they're done in 5-6 mins and never end up tough.