From your link, and going to the more expanded specs from the Rosewill page:
http://www.rosewill.com/products/1799/ProductDetail_Overview.htm
“Active-PFC with auto AC-input voltage adjustment(100-240V)”

It appears that your PSU is equipped with Active PFC (Power Factor Correction), so it falls under the second example I’ve posted above.

To be safe, you’d require a higher VA rating UPS to handle the power. A 1.6 to 2KVA as Unaccptable noted should be sufficient, for the load. That would cover your capacity (load) needs, and run time would ofc depend on battery(s) Ah size.

In addition, due to the PFC, the UPS would need to be “highend/smart” or closer to true sine wave output.


This maybe of help: https://www.dougv.com/2010/03/01/active-pfc-enabled-psus-are-not-compatable-with-most-low-end-ups/
“In short, if you send a high-end PSU the current created by a lower-end UPS, the PSU’s built-in power factor correction hates it, and cuts power to the PC immediately. As in, the exact thing you bought the UPS to prevent in the first place is exactly what happens.

While I understand the value in having a high-performing PSU — less heat, more power, protection for internal components — a straight-up power off of the PC is never a good thing. So your choices are either to forgo a UPS, purchase a really expensive UPS, or purchase a low-cost PSU”