Loading data from on premise Oracle Database to Oracle RDS using RMAN

An RMAN backupset can be loaded directly into RDS. However, you can still use RMAN as a mechanism to move an Oracle database from on premise to RDS.

First, move the data RMAN dump using Tsunami, Aspera, Attunity Cloudbeam, or stand protocols like FTP(s) or HTTP(s) which will be slower. More on moving data from on premise to AWS here: http://cloudconclave.blogspot.com/2013/04/on-premise-application-replication-and.html
OR
You can use Oracle Secure Backup to dump the database directly to S3.

Then load the data into using an Oracle Database instance running on EC2 using RMAN (if RMAN dump on EBS volumes) or Oracle Secure Backup if in S3.

You then load the data into RDS from the EC2 instance using one of the these options:
http://docs.aws.amazon.com/AmazonRDS/latest/UserGuide/Oracle.Procedural.Importing.html

You may ask...why did you go through all this trouble of setting an Oracle database on EC2 when I can simply export/dump the data from the on premise Oracle DB and move to EBS or S3 and then load into RDS.  It is because an RMAN dump is much faster on the on premise side and RMAN produces a more compressed and portable database format to move across the internet to AWS.

You can also use this process to load the data using data pump and Oracle Managed Files:
http://cloudconclave.blogspot.com/2013/10/process-to-load-oracle-data-from-on.html

Native replication for replicating data into and out of RDS has announced in Sept 2012 and details can be found here:
http://aws.typepad.com/aws/2013/09/migrate-mysql-data-to-amazon-rds-and-back.html
This is not yet available for Oracle RDS.