I can't answer for Garmin, but you can request it here using the Garmin Ideas page. If enough users request the same, it's possible it could happen.
Which watch do you have? As a workaround you could use the cross-country skiing profile or edit it to that activity in Garmin Connect after uploading.
There are some "classic" roller-skating apps in Connect IQ, which might be worth a try - Connect IQ Store, which may or may not be any better than using the Inline Skating profile, which is available on some watches.
