Nope, that IS Rod Serling HIMSELF on the screen.
The ToT ride producers scoured the old Tzone show opens to find one that's footage "worked" with what they were trying to do.
They then "rotoscoped" Mr. Serling ("cut around him" in the film, frame-by-frame) so his moving image could be placed (via special effects) into a shot of the elevator loading area.
However, the VOICE is completely replaced by the number-one Serling voice impressionist.
He has been chosen by the late Rod Serling's WIFE as the man who most-closely SOUNDED like Rod.
The voice actor "lip-synced" to the old Serling footage so Rod's mouth is in perfect sync with the new voice.
The film cuts away from Rod right as he says, "...maintenance service elevator." Because in the original Tzone show open, he was NOT introducing a segment about elevators... so from that exact moment on, the lip-sync would not be right.
BTW, in an episode of the TV series "Medium" earlier this season, the producers shot a show (partly) in 3D.
As this show's opening segment, they chose to use a Rod Serling intro from an old Tzone episode.
(The producer must have just ridden ToT at Disney's California Adventure.

)
They hired the SAME voice-actor who we hear at ToT to re-create Rod's voice speaking the new custom script written to go with the 3D "Medium" show.
This time however, they used "computer animation" to RE-FORM the image of Rod's MOUTH to FIT the new script.
It worked pretty well.