Loewe Calida and Roku Streaming

I recently brought out of storeage my beautiful Loewe Calida 2323MB tv. When I used it with cable, I needed to use this adapter to turn RGB component signal into either the VGA or RGB inputs on the tv.

I am trying now to connect Roku Express Plus to the tv. The Roku has composite outputs which fit right into the VCR inputs on the tv, and the results are not HD. To get 1081i HD, do I need to get an adapter for an hdmi cable running out of the Roku and connect it to the KD-Ctca3 and then run that to the tv? Or do I need a converter that can turn the hdmi into component video outs which then connect to the Kd-ctca3?

Oh, I know it is time to think about getting a new tv, but the challenge of getting this to work is keeping me out of the stores and I am glad about that. If I can make it work.
Arthur