Depending on speeds involved, etc., hitting your head while
rollerskiing poses very low risk of serious brain injury.

And hitting your head is a low risk to begin with---depending.

One can get all kinds of whacks and injuries along the whole range of
impact force and serious and still not get a serious or permanent
injury. So it's not like "touch your head to pave' and do not pass
go." You can bang, bleed, crack, break that sucker quite a bit before
she'll say uncle. Smear the face, lose the teeth, tear off the jaw.
Ooo, it's ugly, but all those things heal or you can get used to them
(Hey, I used to be cute, does that count?) And even all these nasty
things are very unlikely to happen in outdoor sports because we
humanoids are darn good at shielding our noggins and also because the
dang things are tough in so many ways. Of course, just the right light
ping can kill ya, too. Takes all kinds.

Speaking of kinds, back when I was a bike racer I thought I'd do a few
rides with the reg'lar folk, take a break from the racer dudes. I'm a
big tent fella and didn't want to miss out on riding slow at the back.
So I went out on a B or C ride for a change once with the touring club
folks. They were older, etc. Man, could they NOT ride bikes! They
wobbled, they fussed, they worried. And when a beagle came barking
down a lawn a bunch of them piled up when he was still 50 yards away.
Musta touched wheels. They all seemed fine to me, though. We got em
sorted out, bikes readjusted, OK let's ride, but no several stayed
sitting and wanted cars to come, phone calls to be made. Everyone was
fine, bikes were fine, but those teeny abrasions worried a couple of
them. I'd never seen such a thing. THOSE folks needed helmets and all
kinds of padding and body armor. Actually they were just plain old at
MAJOR risk being out on the road. Not only to themselves, but think of
the grief they might cause a motorist. And they were the club
officers. Of one of the biggest US clubs. It was funny! In a kind of
dark way.

--JP