If you are not familiar with sampled drum libraries, the idea is to record the drums just as they would be in a typical recording session. In this case, individual drums are recorded with close mics, but also are recorded with overhead mics and room mics. The software used to playback the samples triggers all the different samples (close, OH, Room) at the same time and can be mixed just like a regular drum session. Not only are these drums recorded with the different microphones, but they are recorded at different velocity (soft to loud) levels.
The basic premise of recording the drums this way has dramatically increased the realism of sampled drums since the days of the single sample drum wav file.
The Roots SDX works almost the exact same as the regular SD2 library. If you are familiar to SD2, then Roots will be familiar. Installation takes a long time because there are a lot of DVDs to be copied. You can install smaller versions of the software, but it is kind of silly to purchase the Roots SDX, but then install a `lite' version of the software. If you are worried about you CPU being able to handle the full library, just purchase the Jazz SDX instead. It will save you some money, and the samples come from the exact same recording session. But, if you are a 'tweaker', step up to the big time with Roots SDX.
This library is perfect of jazz/blues styles of music. As the name suggests, it is also the best SDX library if you want acoustic drums for any kind of 'urban' music. Obviously if you want drums for hard rock or metal, choose a different SDX than Roots.
The Toontrack Roots SDX is an expansion library to be used with the main Superior Drummer 2 software. The Roots SDX can be purchased as a 'sticks' only library. a 'brushes' only library, or a combo pack of both. Regardless you need to have SD2 installed to be able to use this SDX because Roots is not a stand-alone software.
There aren't a lot of kit pieces available in this SDX, especially compared to other expansion libraries like Custom & Vintage that have tons and tons of different drums and cymbals. Rather the Roots SDX is fewer kit pieces, but tons and tons of mic channels from the session. For instance, rather than a single pair of overhead microphones, there are multiple pairs of Overhead mics. The same goes for the room mics. There are a full range of Room mics from 'close' to 'distant' providing different levels of ambiance. This is how the library becomes extremely versatile. You can get a dry/tight mix going with one drum kit, but also get a huge drum sound with the same kit if you mix in the room mics.