Rouleaux is not that rare. If it is presenting with the classical characteristic of "stacking" then it's rouleaux, regardless of the patient's diagnosis. On the other hand the simple act of doing the saline replacement, may warm the tube enough to disperse a weak cold. As far as the staff goes, ask them to check each case under the scope prior to reporting rouleaux. As long as clinically significant antibodies are ruled out, the immediate spin XM should present no delaying issues, even if you see reactivity. The first thing I would do is a saline replacement, if neg - issue the blood. Does it matter if it's true rouleaux or a weak cold?