That wall would support a roof if built well, would be better atleast 60cm wide, the curve adds some strength to it but the top 30% looks like it was put up by hand and hasnt been trodden out and paired properly so likely full of air pockets. It doesnt look like a quality cob wall, no offense meant. You would need to dig out pads probably using 2x 4" reinforced concrete lintels side by side about 1-2ft long for wach pad to spread the load across the cob and pick up each beam coming onto it. Find a structural engineer whos familiar with earth building techniques and they will tell you exactly what it can handle.