In a small bowl, whisk together half each of basil and oregano; the garlic, olive oil, vinegar and lemon juice. Before placing the meat inside a resealable plastic bag, lightly score both sides with a sharp knife diagonally against the grain. This will allow the marinade to seep more easily into the meat, and can be used as a guide for slicing later on. Pour the marinade over the meat, massage it onto the meat, seal the bag and refrigerate for two hours; after one hour, turn bag over.
Also after one hour, prepare the "salsa" by lightly combining the tomatoes, shallot, olives and remaining half teaspoon of the basil and oregano; cover with plastic wrap and refrigerate. Add the feta cheese to the mixture just before serving with the meat.
Line a roasting pan with aluminum foil, spray the rack with nonstick spray and insert into the pan. Take the meat out of the bag (discard the bag and excess marinade), place on the rack and place the pan on the center rack inside the oven. After 20 minutes, turn the roast over; after 15 minutes the meat will be rare, 20 minutes for medium-rare. Remove to a cutting board and let it rest for 5-7 minutes to allow its juices to settle within itself before slicing; slice against the grain and thinly. Serve with the Greek "salsa".