It's not possible to stagger the start time that endpoints will connect within a conference.
If you want one to connect later, you'll have to do it manually yourself. With the conference open, click the "Connection Settings" tab and go into the settings for the particular endpoint and set it to use "No Connect" for the connection type. That will prevent this particular endpoint from connecting when everyone else does at the start, but you'll need to manually connect him in TMS when it's time.
Another option is tou could create an entirely separate conference for this particular endpoint, and use the External Hosted option if you're using TMS 14.6 when scheduling it, and enter the address of the other conference. However, I suggest you do not do this because It's messy, as you'll have two separate conferences to manage and there is more room for error.
