Cook the rice according to the package directions.
Meanwhile, heat the oil in a large saucepan over medium heat.
Add the sausage and onions and cook, breaking the sausage up with a spoon and stirring the onions occasionally, for 10 minutes.
Add the tomatoes (and their juices), shrimp, peas, ½ teaspoon salt, and ¼ teaspoon pepper.
Simmer, stirring occasionally, until the shrimp are opaque throughout and the sauce has slightly thickened, 3 to 5 minutes. Serve over the rice.