Roll him back and forth, and then unroll him out. Next time he may be able to unroll himself out. Bring your baby's attention to everyday sounds such as a rain storm, tea kettle whistling, toilet flushing, phone ringing and dogs barking. Tell him what he is hearing. He will learn that sounds help organize and identify his world.
Music is a fine source of infant stimulation and relaxation.
In a Summer Garden, On Hearing the First Cuckoo in Spring. Many libraries will lend classical recordings. Talk to your baby. Look him in the eyes when you speak to him. Give him praise and applause when he has accomplished something.