Any hydraulic roller camshaft that is drilled for LA oiling can be used in your factory roller block with factory roller lifters, within reason and with a few precautions.
The mechanical fuel pump eccentric mounting was already mentioned. If you are running a mechanical fuel pump and LA style timing cover you can use either long snout or short snout. Short snout will require an adapter from Hughes Engines to mount the eccentric.
If using any LA head with standard LA oiling you just need to make sure the camshaft is drilled for LA oiling. They will usually specify LA oiling or Magnum oiling but if they don't the retrofit is usually drilled since most LA engines were not hydraulic roller.
Magnum camshafts are all hydraulic roller and can be used in your LA roller block but they are often times not drilled for LA oiling, so then you have to set everything up for pushrod oiling and use different rocker arms and pushrods. The Magnum camshafts are usually ground for the Magnum factory rocker arm ratio of 1.6, so that also needs to be factored in.
Basically, don't worry about if a camshaft says it is retrofit or not. As long as it is hydraulic roller, has LA oiling holes, and you know if you need an adapter on the front or not.