I think you can catch them after that huge scene with Diagla/Palkia at Spear Pillar, in diamond and pearl.
Earlier, it may seem like you can catch them because the boss released them ,but if you go into one of the lakes, there will still be Galatic Team members and one of the leaders with the plantet names and a bunch of Magikarp laying around outside.
But if you are playing Pokemon platinum, your first time at Spear Pillar will be when you enter whats callled the Distortion World (with Cynthia), where you catch Giratina. I recomand Dusk Balls for that. After you leave Distortion World for the first time, you may go catch Mespirt, Azelf, and Uxie. Those 3 help you through the Distortion World, if you push boulders that you can use Strength on into holes on certain levels of the Distortion World.
But make sure that your Pokemon are healthy because right before catching Giratina, you battle Galatic's boss, Cyrus.
If this isn't true, then at least its a hint. I passed this scene like a few months ago so I don't remember it well.
Battle them.
you have to battle Giratina in distortion world and then you can battle them
battle them i guess
Cyrus will have one when you battle him in the Team Galactic headquarters in Veilstone City.
You go to Vielstone city and go into Team galactic building and find Cyrus(Team galactic boss) then battle him. After the battle he should give you a master ball.
usually i take mesprit azlef and uxie lv 100 each with custom moves
there are three shows and a lot of movies Pokemon dp Pokemon dp battle dimension and Pokemon dp galactic battles
Get the galactic key to get past the door in the Veilstone galactic base and make your way to Cyrus's office and battle him. then he will tell you the warp pannel will take you to Uxie,Mesprit,and azelf. It's been awhile since i have been there but I'm pretey sure you battle the person in front of the button. When you beat him press the button and they go free.
You can play battle revolution with Pokemon platinum.
Pokemon battle platinum
Nobody in Pokemon platinum has a charmander.........
Errrr..if ur talking about mesprit and the others find a room with them in battle the guy and press the button.This is what you do in diamond so it may not work...