The 5th Edition SRD Compendium can only contain information (such as race and class options, feats, spells, treasure, monsters, etc.) that is located within WoTC's Systems Reference Document . Anything else from the core books is licensed material, meaning that players must pay in some way in order to have access to it. You could purchase the physical core books and enter information by hand, or buy them through Roll20 which would give you automated access. Unless you purchase the material, you are limited to the free material provided in the SRD, which is what you see when you come to Roll20. This means you have access to the one sample background in the SRD, the one sample feat, one each of each sub-class archetype, a (generous) selection of spells, and so forth. If WoTC releases more SRD content under an Open Gaming License, you can count on that being added to the Compendium.
