The following should do the job
Code:
Sub macro2()
Dim myRange As Range
Set myRange = ActiveDocument.Content
With myRange.Find
Do While .Execute(FindText:="Roll Call", MatchCase:=True) 'Find the text
myRange.InsertParagraphAfter 'insert a paragraph break after it
myRange.End = myRange.End + 1 'move the end of the range beyond the paragraph break
myRange.Collapse 0 'Collapse the range to its end
ActiveDocument.Bookmarks.Add Name:="mark", Range:=myRange 'add a bookmark at the range
myRange.Select 'optionally select it
Exit Do 'Stop looking for the text
Loop
End With
End Sub