Most of the RPGs I know if are inline or are large in file size - and usually both.
These may fit the bill:
Space Age: A Cosmic Adventure by Big Bucket Software
https://appsto.re/us/RFM-2.i
Or maybe a rogue like would possibly work since they are procedurally generated.
Heroes of Loot perhaps.
Heroes of Loot by Pascal Bestebroer
https://appsto.re/us/NmwdP.i
Dungeon Keeper by Electronic Arts
https://appsto.re/us/aCSsN.i
These is a bit bigger:
LEGO Harry Potter: Years 1-4 by Warner Bros.
https://appsto.re/us/a8Dfy.i
Dungeon Defenders: Second Wave by Trendy Entertainment
https://appsto.re/us/Xgrgy.i
Lili

by BitMonster, Inc.
https://appsto.re/us/d63AH.i
Defenders by NIVAL, INC.
https://appsto.re/us/wOWdP.i
Everything else I could recommend is near a Gig or much larger or is online.
Cheers.