Resolution:
The debug log will show,
"15:24:07 (wrkr) 00000610 t00000f24: debug: IcEvent::recordEvents failed -- &ltError, IC, 124>: Database aborted transaction during deadlock resolution
15:24:07 (wrkr) 00000610 t00000f24: debug: RPC done: 001032 Severity: 3 Time: 1.031 Queued: 0 Database aborted transaction during deadlock resolution."

This only happens with MS SQL server.  The fix to this is to add an index to Roles in the database server.

Add an additional column to the ROLES_JOB_INDEX.  The following command will accomplish this:

CREATE INDEX ROLES_JOB_INDEX ON ROLES ([JOB_ID] ASC, [NAME] ASC) WITH
DROP_EXISTING;

Just to be safe, rebuild the new index, too:
DBCC DBREINDEX(ROLES, ROLES_JOB_INDEX, 0);

Workflow server reports "Database aborted transaction" when doing simultaneous proecess creations.The solution is only know to apply to MS SQL server.