Second Site (SS) handles roles, witnesses, and places the same as TMG with one notable exception: Second Site has inclusion/exclusion logic that can prevent someone from appearing anywhere on the site. If you include _all people_ from your project in your site, then SS will mimic TMG. If you only include a subset, then things get more involved.
First, there are 4 options in the People section that determine whether SS will show the names of excluded people. The options are "Show Excluded Parents", "Show Excluded Principals", "Show Excluded Children", and "Show Excluded Witnesses". If you check all of those boxes, then the results will be pretty similar to TMG.
Also, SS has a "Suppress Details for Living People" option. If you included Living people, and if Suppress Details for Living People is set, then events for living people (Living flag=Y or ?) will not appear (if they are a principal) or they will not be included as a witness (if they are a witness only).
My guess is that you have living people in your TMG project and your SS site is set to Exclude Living.