I do not recommend rinsing....at least not on the same day as the cleaning.  The ideal situation is to let mother nature takes its course but there are situations where the removal process needs to be at least accelerated depending on your customers needs and goals (ie. selling a house, insurance, etc...)  Disclaimer: Rinsing a roof will increase the likelihood to incur granular loss and therefore you will be shortening the roof shingle's overall service life and this is important to educate your customer about.  We have all heard or used the example of using roundup on a weed is similar to soft washing roofs.  And continuing with that analogy when you spray a weed with roundup and were then to try and pull that weed out immediately its hold is just as strong as if you hadn't even sprayed it at all.  However, if you allow time to pass that same weed will become dry and brittle (because its now dead) and you can now remove it with far less force and thus pull it out with less dirt being pulled up or in our situation granular loss.  The rinsing process' goal is not to pull out the lichen's or moss' root system but rather the rinsing process' goal is to sever the moss or lichen from its root system thus leaving the root system still in the shingle.  I would allow at least a few weeks to pass before attempting to use garden hose pressure only to rinse off the now dry and brittle moss and lichens.  If it requires more than garden hose pressure you are damaging the shingle...  Therefore customer education is the key.