separate Roll Explosion part

stepmania/NoteSkins/common/common/Fallback Explosion.lua

@@ -4,6 +4,11 @@ local t = Def.ActorFrame {
 		HoldingOffCommand=NOTESKIN:GetMetricA("HoldGhostArrow", "HoldingOffCommand");
 		InitCommand=cmd(playcommand,"HoldingOff";finishtweening);
 	};
+	NOTESKIN:LoadActor( Var "Button", "Roll Explosion" ) .. {
+		RollOnCommand=NOTESKIN:GetMetricA("HoldGhostArrow", "RollOnCommand");
+		RollOffCommand=NOTESKIN:GetMetricA("HoldGhostArrow", "RollOffCommand");
+		InitCommand=cmd(playcommand,"RollOff";finishtweening);
+	};
 	NOTESKIN:LoadActor( Var "Button", "Tap Explosion Dim" ) .. {
 		InitCommand=cmd(diffusealpha,0);
 		W5Command=NOTESKIN:GetMetricA("GhostArrowDim", "W5Command");

stepmania/NoteSkins/common/common/Fallback Roll Explosion.redir

@@ -0,0 +1 @@
+Fallback Hold Explosion

stepmania/NoteSkins/common/common/metrics.ini

@@ -100,6 +100,8 @@ LiftCommand=
 [HoldGhostArrow]
 HoldingOnCommand=hidden,0
 HoldingOffCommand=hidden,1
+RollOnCommand=hidden,false
+RollOffCommand=hidden,true
 
 [Press]
 ReverseOnCommand=vertalign,bottom

stepmania/NoteSkins/dance/default/NoteSkin.lua

@@ -47,6 +47,7 @@ function ret.Load()
 	-- The main "Explosion" part just loads other actors; don't rotate
 	-- it.  The "Hold Explosion" part should not be rotated.
 	if Var "Element" == "Explosion" or
+	   Var "Element" == "Roll Explosion" or
 	   Var "Element" == "Hold Explosion" then
 		t.BaseRotationZ = nil;
 	end