Rheem doesn't disclose the internal circuitry of their control cards. They expect that field diagnosis will end once confirmed to the card as a whole.
If you think it's the resistor, take a good close up photo of it. If the colors are still discernible, I'll tell you the resistance and wattage and you can get one at any Radio Shack.
As Rheem/Ruud serviceman since the 80's, I seriously doubt that resister is where the issue began. When they begin overheating, the middle lightens to a light brown color (towards the color of thoroughly combusted ash). It doesn't necessarily mean they're bad, they might be just overheated, damaged or simply very old.
You said 'burnt around the same resistors'. That happens often in old cards in the area of resisters more than 1/2 watt in size. It's just the card itself that's burned.