Roof washers (still find that a strange name for water catchers or diverters) are needed for a drinking system. They can be anything from a fancy measured capture system to a valve you turn on and off by hand. A screen or screens to keep most of the big chunks like leaves out pipes and tanks is a real good idea.

If you are using a pressured delivery system then you need a screen filter before the pump. A charcoal filter (taste and chems)and a small/hole size micron filter(dirt or pollen) after the pump or pressure tank. Filtering can be done on just the line/faucet you use for drinking water. I knew of one family that for the first few years filtered their rain water for drinking through a Brita pitcher system. If you are using a gravity flow system then ask your plumbing supply house for suggestions on inline filters or use one of the countertop filtering pitchers.

The two main choices for disinfection (there are others) are UV and chlorine both have their niches. UV on an automated pressure system is great and leaves no residue in the water. This also means that it gives no protection to any of the rest of the system and takes power for the pump and the UV unit. A UV sytem set up for batch disinfection is where you have a UV light that shines in the holding tank for a set amount of time on a set schedule. All the UV systems I have seen were automated. Chlorine is cheap and easy if used as a batch setup but there are many automated chlorine systems out there. It is the main chemical used for public water supply systems. IF you are going to use chlorine(bleach) please be careful and know your math and chemicals. It can be as much of a problem having too much chlorine as not having any. Caution it likes most metals and will eat up a tin tank. It also tends to leave a residue when it combines with organic material. Luckily most of the normal concentrations of chlorine and residues are removed with the charcoal and micron filters. I like a combo setup the best where you have an auto UV and do batch chlorine 2-4 times a year depending on local conditions.

A rain water system can be as easy or fancy as wanted or needed. I grew up with a 55 gal rain barrel that caught water from a roof valley. It was simple and easy. Take the lid off when the water coming off the roof was clear and put it back on when it quit raining. It was what we made coffee, tea or cooked beans with. How good your rain water is depends much on local conditions. How often and what type of rainfall, trees, roof type, dust, pollution in the air from nearby factories and your rain water setup including holding tanks, filters and plumbing all affect water quality.

Enough preaching I did not read the links posted but bet they have all or most of the info I just posted.