Since ITIL is about managing change overall, the release management component would be a piece of the larger ITIL strategy.

For example, not all ITIL requests would require software changes, and in the same vain, not all software changes would involve 'development'. (OS upgrades, adding new functionality for a COTS application etc)

What is important to remember is that the ITIL process would be essentially a wrapper for this component that may have several pieces to it. After this component is executed, the ITIL process would continue with the migration to the end users and notification of resolutions etc.

So essentially you would have ITIL process (change requests) represented as follows: #ITIL Process# [Change activity][Release Mgt][Deployment Activity (includes delivery to end users and training updates etc)]#ITIL Process#

That model is very simplified; however, it does give a representation of the wrapper nature of the ITIL process as it relates to release mgt (as well as other SDLC disciplines and their associated tasks).