Was Roy the only human to board the ship?

Question

At the end of Close Encounters OTTK, Roy Neary gets recruited last-minute into the group of red-suited volunteers that are supposed to go with the aliens. When they approach the ship they line up right in front of the open bay. Roy gets singled out by the race of small aliens and taken up personally. Then the next time we get a wide shot of the ship, the rest of red suits are gone.

While we only actually see Roy boarding with the aliens, did the rest of the group go as well?

You can see the red suits' positioning to the ship in this clip (~00:15).

Then the rest of them no longer in the area in this clip (~01:15).

Answer 1

The astronauts accompanied him

From the film's official novelisation (written by Stephen Spielberg)

Roy turned and took the first step forward. Then he started walking slowly, then faster toward the ship’s negative gravity zone, and the fiery, lighted opening. The twelve astronauts began to follow him.

The little humanoids formed a blinking, twittering file on either side of the column of astronauts and accompanied them up the brilliantly lighted stairway toward the glowing interior of the great mother ship.

One little creature separated himself from the procession and flowed over to Lacombe. He reached out one armlike thing and made the first of the hand signs, corresponding to the first note. Lacombe, deeply moved, responded. Then the creature and the Frenchman went through the other four hand signs.

Lacombe looked down into its . . . face. It was changing—from something embryonic, unformed, into a face of something a thousand years old. Suddenly, Lacombe knew that all the wisdom, all the superintelligence, the experience that it had to take to build these vehicles, to travel these dozens of light years was there in the aging countenance and the . . . yes, the smile of this fantastic little creature.

Lacombe smiled back, and then the little thing flowed away after the others into the phantom ship. Neary was almost inside now. Incredibly, he was thinking and hearing a song in his head. It was from Pinocchio. When you wish upon a star, Makes no difference who you are. Anything your heart desires will come . . . to . . . you. He took another step up the ramp of fiery brilliance into the center of the starship. Around him the blaze was almost blinding, yet he seemed to be able to see . . . everything. And the music in his head grew louder. If your heart is in your dream, No request is too extreme, When you wish upon a star as dreamers do.

Roy turned to make sure the twelve astronauts were still with him. Then he waved one last time to Lacombe and to Jillian and Barry. He hoped they could still see him. Outside, on the cement strip, the figures of Neary, the astronauts, the little creatures, were dematerializing into fiery light and energy.

And from the film's screenplay

_{^{"The inside light burns brighter and brighter as one after another the twenty volunteers disappear into the brilliant opening"}}