Rinse the rise in a fine mesh strainer under cold water until the water runs clear or mostly clear. It should take 3 to 5 minutes. Note: This step is optional, but rinsing the rice will remove excess starches on the outside of the rice, which helps you get fluffy rice rather than sticky rice.
Combine the water, roasted chicken base, rice, and butter in a medium sauce pot (I use a 3-quart sauce pot). Bring to a boil over medium-high heat.
Cover the pot, reduce the heat, and simmer for 15 to 20 minutes, or until the rice is tender and the liquid has been absorbed.
While the rice is cooking, cook the frozen mixed vegetables according to the package directions either on the stove top or in the microwave. Drain any water.
When the rice has finished cooking, remove the pot from the heat and let it sit, covered, for 5 minutes.
Fluff the rice with a fork, add the cooked mixed vegetables, and stir to combine. Add salt and pepper, to taste, if desired.