I used precooked homemade brown rice, and I purchased precooked lentils. Gotta say that they were great.
Start by cooking the rice since it takes the longest. In a small saucepan add the rice and 2/3 cup of water. Bring to a boil with a piiiiinch of salt. Reduce to a simmer, cover, and cook until tender- about 40 minutes.
Meanwhile also cook the lentils. In another small saucepan add the lentils and a cup of water and prepare the same as the rice, but they should only take about 20 minutes. Add more water if they are too dry. The cooking time on lentils depends on how old/dry they are.
Steam the edamame for 5 minutes and set aside.
When everything is ready place the rice, edamame, lentils and arugula in a large bowl.
In a small bowl combine the lemon juice, rosemary and mustard. Stir smooth. Slowly add the oil while constantly stirring the dressing. Add salt and pepper to taste.
Pour the dressing over the salad (dressing warm rice and lentils is perfect) and serve.