I got a e-mail from the Hyatt Regency Osaka, and they say that they will increase the hotel shuttle bus between the Hyatt Regency Osaka and JR Osaka station from September. The timetable is below.
From HRO to JR Osaka station
8:00 / 9:00 / 10:00 / 11:00 / 11:30 / 12:00 /
12:15*/ 12:30 / 13:00 / 13:30 / 14:00 / 14:30*/
15:00 / 16:00 / 16:30*/ 17:00 / 18:00 / 18:15*/
18:30 / 19:00 / 19:30 / 20:00 / 20:15*/ 20:30 /
21:00 / 21:30 / 22:15*
From JR Osaka station to HRO
8:30 / 9:30 / 10:30 / 11:00*/ 11:30 / 12:00 /
12:30 / 13:00 / 13:15*/ 13:30 / 14:00 / 14:30 /
15:15*/ 15:30 / 16:30 / 17:15*/ 17:30 / 18:30 /
19:00 / 19:15*/ 19:30 / 20:00 / 20:30 / 21:00 /
21:15*/ 22:00
" * " mark is only on Sat, Sun and holidays.