<p>I need to send an email to someone and want them to be able to simply reply to the email without having to specify the email address.</p>

<p>Using sp_send_dbmail sets the reply-to address as the name of the profile that it was sent from.</p>

<p>Can this be changed to specify the reply-to so it looks like it came from me.</p>

<p>Thanks.</p>

Not in sp send dbmail itself
The reply address is just text and can be set up in the profile.
Eg I configure bob@bob.com but the email account is private@isp.com
Hit reply and it goes to bob@bob.com
So, configure your profile used by the sp thus to show this.
The line saying "The e-mail address to show on outgoing e-mail messages." here
sp send dbmail help. no parameter for reply address