Forward fold. Fold from the hip, keeping your knees as bent as you need for comfort. If you hold this stretch for multiple breathes, think of flattening your back and gently deepening the stretch on the exhale. Bonus: cross your feet and do this stretch.
Lateral stretches: clasp your hands over your head and stretch to one side, then the other side. You may not think that this is related to your hips, but it can be!
Lunges. You can make them a dynamic stretch by slowly rising up on your back toe and then dropping your heel back down. Turn them into a hamstring stretch by straightening the front leg, and if you have the time and space, reach down to your forward shin or ankle to go into triangle pose.
Stand on one foot and pull the other knee to your chest.
Stand on one leg and cross the other foot over the front of your knee (or thigh if you can), then fold forward from the hip. You can also do this one sitting.
When you’re home, use that foam roller on your quads, hamstrings, adductors and gluts too.
(Remember that the effects of stretching happen in very small increments. Kind of like dressage.
You won’t notice at first, but after 6-8 weeks of consistent stretching, suddenly you’ll realize that you are more limber than you were when you started. Learn what a good stretch feels like and don’t push further than that.)
One of the best things you can do is take a series of yoga classes. This will give you a library of stretches, and teach you both the best way to do them and the modifications you can use to make them either easier or more difficult.