gistfile1.cs

var tree = CSharpSyntaxTree.ParseText(@"
  public class MyClass{
	  #region MyRegion
	  #endregion
  }");

//Try finding them as nodes.
var regionNodes = tree.GetRoot().DescendantNodes().OfType<RegionDirectiveTriviaSyntax>();
//Try finding them as trivia? 
var regionTrivia = tree.GetRoot().DescendantTrivia().OfType<RegionDirectiveTriviaSyntax>();