I am certain in Google Ads your bid adjustments are ignored when using ROAS. There is one exception, that is when you adjust -100% against a device Type (Cell, Computer, Tablet). To the best of my knowledge that is the only bid modifier that is allowed when using tROAS.
Not exactly your question but I suggest not using target ROAS on bing in most cases. I stick with enhanced CPC and prune the bad keywords.
If it worked on bing then great but usually doesn’t unless you have some massive amount of data or whatever