Placing your entire spine solidly against a wall with your feel a foot away from the wall is a great way to safely lengthen your spine and get connected with your powerhouse.
Doing the roll up on the mat can be challenging. Sometimes it is difficult to feel that your are rolling with control and feeling each vertebra touch the floor as you roll up and down. keeping your feet solidly on the mat is a whole different challenge. Using the wall in combination with your breath to accomplish proper rolling and use of the powerhouse is very effective and can also work to expand your lung capacity.
Inhale as you gently drop your head forward letting the weight of your head slowly roll the body forward exhaling as you round forward, arms hanging. Inhale as you roll up engaging your powerhouse and sliding back up the wall. Practice articulation of the spine from the front of the body!.