Bring a large pot of heavily salted water to a boil. Add the spaghetti and cook according to the package directions.
While the pasta cooks, start the sauce. In a large skillet heat the olive oil over medium heat. Add the garlic and cook, stirring, for 30 seconds. Add the lemon zest, lemon juice, peas, ricotta, and Romano cheeses. Stir and cook gently until the peas are heated through and the sauce is smooth.
Drain the spaghetti reserving about a cup of the cooking water. Add the spaghetti to the sauce and toss gently to coat. Add some of the reserved pasta water to the sauce, ¼ cup at a time until the sauce is thinned out slightly and completely coats the spaghetti. Season to taste with salt and freshly ground black pepper.
Just before serving, stack the mint leaves, roll up like a cigar, and slice thinly. Add to the pasta and toss gently.