Gates, 29, is a former fourth-round pick of the Dolphins back in 2011. However, he lasted just two years in Miami before he was waived and later claimed by the Jets.
Gates spent a little over two years with the Jets before he was once again placed on waivers. The Titans elected to sign him to a future/reserve contract back in January, but elected to cut him loose in recent days.
Smith, 28, originally signed on with the Packers as an undrafted free agent out of Arizona State back in 2013. He lasted just a few months in Green Bay before he was waived at the start of the regular season.
Since then, Smith has played for the Bills and Jets before signing a two-year contract worth $1.11 million with the Cowboys a little over a week.
Smith last appeared in an NFL game during the 2013 season, but has yet to record a single statistic.
Johnson, 23, is an undrafted free agent out of Kansas State who signed on with the Seahawks a few weeks ago. However, he lasted just a few weeks with the team before being released earlier in the week.