Heat the oven to 300° F. Drain and roughly chop the tomatoes, then toss with the olive oil, garlic, and optional herbs. Salt to taste. Spread the mixture in a large baking dish or a rimmed half-sheet pan -- the more cramped it is, the longer it will take to roast -- and roast for approximately 2 hours, turning occasionally, or until the tomatoes are sweet and rich and just beginning to dry out.
Bring a pot of salted water to boil. Add the farro and cook it until al dente. Drain the farro and then toss it with the roasted tomatoes and garlic; add more olive oil if necessary. Shower with Parmesan cheese and serve.