Jeff,
There have been a number of alternatives on the ventilation. Basically, residential units want to take air from the bottom, run it through the condenser coils and out the back where it is expected to flow up the back and out the top of the refer. S&B homes do not have vents right over the back like RVs do. So, you can do whatever here. I chose to leave a bit of space over the refer (some of which I may close with molding later), seal the top vent and let the hot air return to the room for the air conditioner to take out. You may want to leave the roof vent open to let the hot air escape there. Just be aware that cold air can come in during the winter and hot air may creep in during summer if you leave it open.
If you have a Samsung unit, they also run some of the piping along the outside walls of the refer and count on some air circulation up the sides and out the top. Depending on your unit, you may need to be sure there is air-flow here too.