Here, I think I found what youre looking for on gamefaqs... o.o Otherwise I have no idea what you want help with xD There is no Rocket thing on Island 4 anyway, it is Island 5 o0
As soon as you enter, you will see this is a puzzle just like the one in the
other Rocket Base at the Game Corner, and Giovanni's gym. I guess it must be
the Rocket's trademark puzzle now, eh? Well, this one's a bit more complicated
than the others. You have to remember that you can only turn when you see an
arrow pointing another direction if you spin into it, now below. I made this
mistake a lot. You also keep going even if there are no arrows.
When you first get inside, take the left arrow. Go all the way up and collect
the Upgrade. Now go past the female Rocket grunt and take the down arrow
towards the left. Walk up and defeat the rocket, then take the left
transporter in the middle. From there, walk all the way up the path and get
TM36. Take either one of the two transporters that goes down two spaces and
fight the Rocket holding two Level 49 Hypnos.
You're almost there now! Take the only transporter and fight the female Rocket
holding a Level 52 Muk and a Level 53 Arbok and Vileplume. When you defeat
her, she will activate a machine than changes one of the arrows at the bottom
to point up so you won't have to go through all that work to get back there.
Now, go fight the next Rocket! He will have a Level 53 Golbat, Level 54
Weezing, and Level 55 Houndoom. After this, all the Rockets will disappear
leaving only one, the Scientist who stole your Sapphire Plate! This guy's a
joke so don't worry about him too much. He'll have a Level 46 Voltorb,
Electrode, Magnemite, Magneton, and Porygon.
After you get the Sapphire Plate, go back to Island 1 and give it to the man.
You will now be able to trade with Pokemon Colloseum and Ruby and Sapphire!
You will also have access to the Unknown Dungeon.