Vegetables are super easy! I like getting the ones in those steamer bags, but you can buy fresh broccoli and carrots and whatnot, steam/roast them at home, then just pop them in the microwave to warm up once you get to work. Some easy sauces like teriyaki or even just lemon and salt and pepper are awesome on veggies.
Chicken breasts and thighs are super easy to make at home, and they heat up well in the microwave. All you need to do is slap them in a pan on the stovetop or even just something you can put in the oven, add seasoning, and you're good!