Gigabyte was not the only one with a Mini-ITX AM4 motherboard at Computex, ASRock actually had two. The one we are really interested in is their X370 Gaming-ITX/ac, which of course is built with gamers in mind. The small board features a black and red design with ASRock and Fatal1ty branding on one of the heatsinks.
Of course the AM4 socket takes up most of the board itself. You also have a single PCI-Express 3.0 x16 slot, two DDR4 DIMM slots with support for up to 3200 MHz memory, four SATA 6GB/s ports, and a USB 3.0 header. There is no mention of an M.2 slot, although it could be on the backside of the board.
When it comes to the rear I/O you have two USB 2.0 ports (one is the Fatal1ty mouse port), 2 HDMI, four USB 3.0 (3 type-A, 1 type-C), Gigabit Ethernet (Intel powered), audio connections, and the antenna connectors for the WiFi. The board also has Intel-powered 802.11ac WiFi / Bluetooth 4.0.