Turns out the Pot Roast was undercooked.

Long believed to be a natural fit for the Raiders, free-agent defensive tackle Terrance “Pot Roast” Knighton said Tuesday that he will not be rejoining former coach Jack Del Rio in Oakland.

Knighton had followed Del Rio from Jacksonville to Denver, and the run-stuffer had expressed an interest in joining the coach again, but negotiations ended Tuesday afternoon.

“The Raiders made me an offer, but it’s not close to what I was looking for,” Knighton told ESPN. “So, as of right now, the Raiders … are out of the race.”

Knighton, 28, started every game for the Broncos the past two seasons and was said to be seeking $8 million a year. The Raiders were thinking closer to $6 million, considering Knighton comes off the field on 3rd-and-long downs.

Oakland was looking at Knighton or Arizona’s Dan Williams as Plan B to Ndamukong Suh, the prize of the free-agent pool who signed with the Dolphins. Williams visited the Raiders on Tuesday night and is expected to sign.

The Raiders came into NFL free agency $66 million under the cap, but have only one new impact starter to show for it. Oakland agreed to a five-year, $44.5 million deal with former Kansas City center Rodney Hudson on Monday.

General manager Reggie McKenzie did add three role players Tuesday. Outside linebacker Malcolm Smith, the Super Bowl XLVIII MVP for the Seahawks, could compete for a starting job at middle linebacker, and former Buffalo tight end Lee Smith is an accomplished blocker.

The Raiders also agreed to terms with backup running back Roy Helu, who spent his first four seasons with Washington. Helu is getting $4 million for two years.

The Danville native had 42 receptions for 477 yards and two touchdowns, and 40 carries for 216 yards and a touchdown last season. Helu provides a different look than running back Latavius Murray and fullback/H-back Marcel Reece in new offensive coordinator Bill Musgrave’s up-tempo offense.

The Raiders also are close to signing former Cincinnati tight end Jermaine Gresham, who also visited Tuesday night.

Malcolm Smith, 25, played for new Oakland defensive coordinator Ken Norton Jr. last year in Seattle. Smith started five games last season after he won Super Bowl MVP honors for returning a Peyton Manning interception 69 yards for a touchdown.

Lee Smith, 27, signed a three-year, $9 million deal.

Vic Tafur is a San Francisco Chronicle staff writer. E-mail: vtafur@sfchronicle.com Twitter: @VicTafur