Depending on the school you train at, different amounts of emphasis may be placed on drilling and rolling. Although this is subject to debate, both have great merits.
The way I look at it is like this:
Rolling is only effective once you actually know what you are doing. If you are so brand new that you can't even demonstrate a move with accuracy against a drilling partner, then drilling is more beneficial.
Drilling is the precursor to rolling, and a considerable amount of time should be spent getting the techniques clean.
When a teacher shows a technique, often times it is like playing a game of telephone, where the students only retain some of the details.
A good practice would be to remember the technique you learned in class, and then look it up online later to catch details that you may have missed.
Now a back take from the de la riva guard.