insted of this
SLRequest *twitterRequest = [SLRequest requestForServiceType:SLServiceTypeTwitter requestMethod:SLRequestMethodPOST URL:[NSURL URLWithString:@"https://api.twitter.com/1.1/statuses/retweet/%@.json"] parameters [NSDictionary dictionaryWithObject:tweetId forKey:@"id"]];
try this
SLRequest *twitterRequest = [SLRequest requestForServiceType:SLServiceTypeTwitter requestMethod:SLRequestMethodPOST URL:[NSURL URLWithString:@"https://api.twitter.com/1.1/statuses/retweet/%@.json"] parameters:[NSDictionary dictionaryWithObject:tweetId forKey:@"status"]];
one thing u can not repost the same message again and again it will consider as spam
and also see this link probably u may miss something