The adductor muscles are the muscles that run along your inner thigh. Tight adductor muscles are a common reason why people feel tight in the hips. Tight adductors can inhibit your glutes which can affect compound movements such as squats and lunges. Keeping the adductors loose is very important for hip mobility and to obtain the proper form of lower leg exercises.
To foam roll the adductors, you are going to have to get into an awkward beginning position. But it works.
Read the general instructions on how to foam rolling, here.