Setting riches as a goal can only mean that one is not free to pursue the higher more coveted goal of godliness. It is the desire, not the riches that proves the obstacle. A root is that which anchors and is the source of life. When the love of anything replaces the love of God, one's salvation is jeopardized. When love for God is displaced as the sharpest desire and drive of one's life, trouble sets in.
Riches is an obvious choice.
It is elemental. It certainly would rarely be the thoughtful person's choice. Paul discloses in this discourse that some had already illustrated the pattern. They erred from the faith, and pierced themselves through with many sorrows. Their salvation was lost, and unhappiness was their lot.