Dell takes stock of the situation, his mind going into triple gear as he's trying to solve this new quandary: "This whole thing works like a clock... let's see: everytime we push one of these doors whoever's in the bigger room gets whacked by magic. Small whacks,  but still, bound to whittle us down...". Barry sees the rogue's lips move soundlessly as Dell's trying to make sense of the whole thing, apparently lost in thought deep inside himself. 

 "Okay, we may as well try this...", he says under his breath after a moment, snapping back to attention and shouting at Velkyn in the bigger room: "Velk ! Look let's try something...! There's FIVE of us and FIVE small rooms, yeah ? Maybe if one of us stands alone in each of the small rooms...? See what happens then. Only we'd have to coordinate our moves to avoid anyone being smacked about with these nasty magic bolts again, you feel me ?". Slowly, a wide grin appears on his face as he looks straight at Barry, who's watching the rogue, wide-eyed and mouth agape.

"Say, Master Dwarf... ever played 'Musical Chairs'? It's fun, ye'll see... I'll explain, c'mon here."

Dell figures if everyone in the group including Grexx and Ryinor manage to position themselves inside each one of the smaller rooms, there might be something to be learned somehow(or then again maybe not...). In any case this idea could run as follows:

-Velkyn gets into the small eastern room with no door

- Barry  moves three rooms clockwise (so reaching the last small cubicle before the big room) while Dell moves two (reaching the one underneath, meaning south of Barry's room).

- Either Grexx or Ryinor enters the big room by himself. No-one else moves. He gets into the second small room, east of Dell's.

- Whoever's last gets into the last room available.

Then the group sees if anything happens.

So Velkyn is already in 1

Barry and Dell are in 3,

who is moving where?

Grexx sprints into 5.  Riynor will enter 3 once it is available.

I'll say you use your knowledge of when the bolts shoot to get into the rooms without getting hit.

Grexx, give me a Perception check

Perception:  20

Barry will go to room 2.

Grexx do you have the goggles?

Yes, but have not had time to attune

Whatever. Just use em.

I told you where you found them that they just worked when you put them on.

Dell will be waiting in room 1.

Ah!  Very good.  That makes my roll a 3 then.

It gives you advantage on sight based checks

Ah!  Second roll then!

15

Grexx it looks like the southern wall in your room might open, but you can't tell how.

Grexx tries to push it.  Does it wiggle or show any signs of give?

Strength:  16

It wiggles a little, it looks like it can only be opened a certain way.

So Grexx quickly figures out he can push the wall down into the floor revealing another small room. After some investigation he sees that room has a fake wall that rotates into the wall. a couple other things happen and he makes his way through a series of tiny rooms with no issues and pops back out into a room that he recognizes from his travels through the arch

Here is what he sees for the rest of you:

You enter in to a long tunnel of a room. At first you think you've made your way back to the first room yet again. But a quick look around reveals that this room is different. Although the floor is the same colourful mosaic, there is no red path in this room.  Also the images on the wall are different then the last room. There are humanoid creatures and animals in various scenes, but incorporated all around are images of large spheres of different colours.

The images of the spheres are what stand out the most in this room, they are flat and 2 dimensional of course but are painted to look 3D.  You emerge from a secret door near the North end of the tunnel which heads South. Starting from where you are and going down the West wall the sphere's are Gold, Orange, Purple, Bronze, Gray, Bright Blue, White, Turquoise, Scarlet, and Pale Green.  going in the same direction but on the East wall, they are: Pale Blue, Silver, Green, Yellow, Pink, Black, Pale Violet, Red, Buff (like a tan or pale yellow), and Indigo.

Also on the far side, you see an archway that looks just like the one from the last room, but its on the far wall where the demon face was in the last room.

There's also a small hallway just across from you that bends off to the West.

Grexx will go back to the room 5 with the and yell to the others that he has found the way.

Back in his small room, Dell yells back: "Okay, wait for us, we'll go one by one to avoid being shazamed again...!"

With, he carefully pushes his door into the big room open, waiting a moment behind the threshold, to make sure that no magic is being cast his way. Then he'll shout at the others in the rest of the rooms:

"Okay everyone, I'll go first...! Wait for the signal  that I got to the other side safely before you open any of your doors !", then after a second he adds: "Barry: RED LIGHT ! DON'T DO ANYTHING YET, OKAY ?".

Finally, after making sure that all is safe, he'll sprint towards Grexx.

Let's just say you all use the same method to get to the other room.