Heat oil in 12-inch skillet over medium heat; add sausage and cook and stir, crumbling into small pieces, until cooked through and no longer pink, 5 to 7 minutes. Remove cooked sausage from skillet with a slotted spoon; drain on paper-towel-lined plate. Pour off all but 1 tablespoon rendered fat.
Place mushrooms in skillet and cook over medium heat until tender, 2 to 3 minutes. Transfer from pan with slotted spoon to plate with sausage.
Prepare Knorr(R) Rice Sides(TM) - Herb & Butter in skillet according to package directions. Stir dried Italian seasoning into the water; omit additional margarine. Three minutes before the rice is finished cooking, add the peas. When rice is done, stir in cooked sausage and mushrooms. Heat through.
Add romaine lettuce and tomatoes; toss lightly. Scoop into serving bowls; top each serving with desired amount of shredded cheese and serve immediately.