You do not meet Riley more than once in Pokemon Diamond version. You only meet him once, and that is at Iron Island. You don't see him anywhere else.
the elite four. battle them over and over again or go to Iron Island. It might help!
you wake up in your house again
Get a team that can win once; they will only get better as you defeat the league again and again.
no only leaf and fire
Bill will appear after beating the 7th gym leader he will let you go to one island lets say you say NO he will go in the cinnibar island Pokemon center talk to him again and say YES to go to island 1.
Riley is a character in Pokemon. He is found in Diamond, Platinum and Pearl versions. http://pokemon.wikia.com/wiki/Riley
To get rid of Riley, you'll have to leave Iron Island. But if you walk into it again, he'll accompany you. There's no way to get rid of him once you're inside so you'll just have to travel to the end of Iron Island with him.
Go to Canalave city, and talk to the sailor next to a boat, he will take you to Iron Island. Next enter the cave, there are to sides that you can enter, take the right side, step onto it take the right side. Go through there until you see another elevator and take the left side again. There you will see Riley, walk up to him and he will go with you, keep going until you see to team galatic grunts, battle them and after you beat them Riley will give you an egg. Note: After Riley gives you the egg he will not appear in the game again.
in iron island go to the right side and you go down and down and you meet.... Riley! Riley asks you to help him get out the cave. and battle with other people but Riley battles with you! he gives you a egg. after you get the egg go down again and you find a shiny stone!
diamond jubilee again
The oil can is used to oil the gears of the clock in the clock tower at Diamond Plains, so that the clock will work again.
when you get the national dex talk to the sailors kid in canalave(the sailor who takes you to iron island) when your done talking to the kid talk to the sailor again and hell take you there.
bobryley.com
the elite four. battle them over and over again or go to Iron Island. It might help!
It's You Again - 2012 The Meeting 1-2 was released on: USA: 25 January 2013
You have to talk to the man that takes you to iron island and make him go to fullmoon island. Go upwards and you will find a Cresselia dropping feather i don't remember the name of. Then you will have to talk to the boy again and he will be cured.
Neil Diamond--- Hello Again - 1986 TV was released on: USA: 1986