Oats must be steamed (cooked at least a bit) in order to roll them.
Quick-cooking oats are steamed more than 'old-fashioned'.
Cracked or steel-cut oats are uncooked.
Oats are an unusual grain in two respects. First, they are
sufficiently complete nutritionally that one can live off
nothing else for several months. This was vital to know in the
days of crossing the Atlantic in the days of sail, when bad
weather could easily add a month to the travel time. In the
early 1800's, my Wallace and Watson ancestors came from Liverpool
to Canada without a single fatality, at a time when official
fatality rates were 20% for emigrants and actual rates at
least double that. With the advice of the British government
of the time, they filled one of their bunks with oatmeal to
be sure of having food to last any voyage. (Family records
simply used the word 'oatmeal', so I don't know whether it
was cracked or rolled.)
The second unusual fact about oats is that we can digest it
uncooked, as noted by others - just soak it overnight. This
was also vital during stormy weather when sailing ship
passengers would be locked below decks under battened
hatches, with no fires possible.
I confess to cooking my oats - bring them to the boil the
night before, set them aside on the stove, then have them
for breakfast. If you are heading out for a full morning's
work outdoors, oats are great food.