Added docs for Baggy.roll. Most text from S32

Author: Jan-Olof Hendig

doc/Type/Baggy.pod

@@ -29,7 +29,31 @@ L<Mixy>.
 
 =head2 method roll
 
-=comment TODO
+Defined as:
+
+    multi method roll(Baggy:D:) returns Any:D
+    multi method roll(Baggy:D: $count) returns Seq:D
+
+Like an ordinary list L<roll|/type/List/#routine_roll>, but returns keys of the invocant weighted
+by their values, as if the keys were replicated the number of times indicated
+by the corresponding value and then list roll used. The underlying
+metaphor for rolling is that you're throwing C<$count> dice that are
+independent of each other, which (in bag terms) is equivalent to picking
+a colored marble out your bag and then putting it back, and doing this
+C<$count> times. In dice terms, the number of marbles corresponds to the
+number of sides, and the number of marbles of the same color corresponds
+to the number of sides with the same color. (For "picking without replacement"
+see L<pick|#method pick> instead).
+
+If C<*> is passed to C<$count>, returns a lazy, infinite sequence of randomly
+chosen elements from the invocant.
+
+    my $breakfast = bag <eggs bacon bacon bacon>;
+    say $breakfast.roll;                                  # bacon
+    say $breakfast.roll(3);                               # (bacon eggs bacon)
+
+    my $random_dishes := $breakfast.roll(*);
+    say $random_dishes[^5];                               # (bacon eggs bacon bacon bacon)
 
 =head2 method classify-list