I think not all of these allow inline skates. Ive seen them only at the last two. https://temple-hills-skate-palace.business.site/

https://lanhamskatecenter.com/

https://laurelskatingcenter.com/

https://skatenfunzone.com/

https://www.nps.gov/anac/planyourvisit/roller-skating.htm

https://www.sk8zone.com/

I see inline skaters the most on the mount vernon trail but that is because of where i live. https://www.nps.gov/gwmp/planyourvisit/mtvernontrail.htm

There are probably other popular places right in dc.