Rough start as in it only takes 1 try to get it going but it runs really rough at first or rough start as it takes 2-3 times and cranks alot to make it fire up? My old Taurus SHO did one or the other or sometimes both and it was just a bad cam position sensor. When that sensor goes, the motor doesn't know where the cam is in relation to what the firing order should be so it just randomly starts lighting off cylinders which means it could start right up or it might take multiple tries and then when it does finally catch it could be rough for a few seconds and then smooth out as the computer figures everything out.