Richardson is a running back from Abilene Christian known for his speed. Watkins is a South Carolina product who figures to be in the competition for the team's starting left guard job.
That brings the total number of rookies signed this week to four. Richardson and Watkins deals follow news earlier in the day that 4th-round pick Chris Givens and 7th-round pick Aaron Brown signed contracts. Six draft picks remain unsigned.
Credit goes to senior assistant Tony Pastoors who has been working to get the deals done, according to the Rams.
Prior to Friday, the Rams were one of four teams that had yet to sign any of their draft picks. Last week, general manager Les Snead told the media that deals were likely to start happening this week. The team had said before that there was no rush, given that the details of the deals are spelled out in the rookie wage scale that was part of the 2011 collective bargaining agreement.
The Rams are working on deals with their other rookies.