Centre-back Robertson has arrived from Preston on a two-year deal while out-of-contract striker Tomlin will join up with his new team-mates on July 1 having finished as top scorer at Southend last season with 16 goals.
"We've been after a new centre half and Chris fits the bill," Adams told the club's official website.
"He's 6ft 3in, has got good experience in League One at Preston and is going to be a decent addition to the squad."
Following completion of the deal, Robertson was equally happy to have signed and was in confident mood about Vale's chances for the coming season.
"The club is on the up and there is a good atmosphere around the place at the moment with regards to the promotion last year, I am ready to get stuck in," the 26-year-old added.
Joining Robertson at Vale Park is 30-year-old Tomlin.
"The manager showed a massive interest in me," the London-born striker said.
"I was always told by friends and fellow experienced professionals that you have to go where you are wanted.
"Getting promoted, you've done really well last season, it's a good team and you've got some really exciting players so it's a pleasure to be here."