What I love about the ab roller exercise is that it's an isometric core exercise WHEN performed correctly. Focus on keeping your torso tight as you slide your arms forward until you'll lose quality of the movement, then stop. Slowly return to starting position and repeat!
As described by Benjamin Lee and Stuart McGill 2015, "Core exercises are a staple among athletically trained individuals and clinical populations in an effort to strengthen musculature, reduce low back pain, and improve sport performance."
Greater torso stiffness enhances performance three ways as explained by Dr. Stuart McGill,
1) Stiffening the torso transfers the full force and movement of muscles distal to the shoulder and hip joint RESULTING in greater limb strength and speed.
2) Muscularly stiffening the spinal column enhances load bearing capacity preventing buckling.
3) Muscular turgor associated with stiffness creates an armor over vital structures enhancing resilience during contact sports."
Article: Effect of Long-Term isometric training on core/torso stiffness