Views Page Title Based on URL
Since you're using Views and the user name. All you need to do is:

Add a Contextual Filter, User: Name
Under it's settings pane, under WHEN THE FILTER VALUE IS IN THE URL OR A DEFAULT IS PROVIDED, check Override title
Then just input %2

So now /person/jon-doe/roster would display as jon-doe as the page title.
If you would want the user's normal name like Jon Doe, then you could follow Immanuel Paul's answer because you aren't basing the page title literally from the URL.