For the ones who are still struggling on this issue:
FTexture2DRHIRef Texture = RHICreateTexture2D(SizeX, SizeY, PF_A32B32G32R32F, 1, 1, TexCreate_ShaderResource | TexCreate_UAV, CreateInfo);
FTexture2DRHIRef OriginalRT = OutputTargetResource->GetRenderTargetTexture();
FUnorderedAccessViewRHIRef TextureUAV = RHICreateUnorderedAccessView(Texture);
ComputeShader->SetParameters(RHICmdList, TextureUAV);
DispatchComputeShader(RHICmdList, *ComputeShader, SizeX / 32, SizeY / 32, 1);
ComputeShader->UnbindBuffers(RHICmdList);
// Now parameter Texture saves the execute result
FRHICopyTextureInfo CopyInfo(SizeX,SizeY);
RHICmdList.CopyTexture(Texture, OriginalRT, CopyInfo);
This Key is to make the FRHICopyTextureInfo struct and then CopyTexture function works, OriginalRT then works for material use