The ROM is irrelevant, the 5170 board is physically wired that way.
You can relocate the adaptec boot rom with either jumpers or dip switches depending on the exact card model. I'd suggest moving it to C800
The original 5170 AT had the E segment of UMA hardwired to ROM sockets on the motherboard, as such many clone boards did not make this segment addressable on the ISA bus. That may be your issue. I'd suggest trying to move whatever ROM is currently at DC00 to the C segment after the video ROM.