There is a new weed killer available with a favorable environmental profile, and works during colder weather (although slowly).  It is called Finale, and contains an amino acid (biodegradable) that causes the weed to be unable to rid itself of metabolic by-products (wastes).  The plant slowly poisons itself, as if it's liver quit working.  The Finale breaks down in the soil quickly.  It is similar to Roundup.

March is the ideal month to plant a new lawn, or reseed bare spots.  Growing grass seed is easy if you know the trick - constant moisture.  Where most people go wrong is letting the seed dry out for a day.  Once the seed is watered, it swells and breaks out of the seed coat making a "sprout".  If the sprout dries out it dies very quickly - so once you plant the seed, never let it dry out!  It really requires that it be moist 24 hours a day until you see that it is rooted well enough to get some water from the soil.

You had better get the moss off of your roof before it ruins it.  If you let it go, it really breaks down the roofing material, shortening the life of your roof by as much as 75%.  At $5,000 or more for a roof it is worth it to hire someone to clean it, or you can get on the ladder and do it yourself.  First kill the moss with one of the many moss killers containing zinc, either liquid or dry formulations.  Wait a few weeks for the moss to die, and pick a day after a dry spell to brush it off.  It comes off fairly easily if it is dead and dry.  The same cannot be said for lush green moist living moss!  Be as gentle as possible with your roof - you do not want to dislodge much of the "sand" coating of a composition roof.  NEVER use a pressure washer on roofing materials - it will ruin them.