This is the order. 1) you’re missing bridge pieces. You either need those or a new bridge. Got it? Check. 2) you have a zero fret. The nut slots have to be deep enough that the strings are forced down on it, just like a bridge break angle. Got it? Check. 3) the distance from the zero feet to the 12th fret and the distance from the 12th fret to the center of the bridge must nominally equal. Got it? Check. 4) if the bridge is floating, it can be nudged and angled to get the intonation better. If you buy a Bigsby like @BorderRadio suggests, even better. But a zero fret and a roller bridge is no different than my 1967 Gretsch. That intonation is fine.