How cool, I considered making one just as you described.
However, I opted to buy a 4 ft. poly roller from Sears. Not sure if it was the best decision though. At the time I bought it it was early spring and I wanted to roll out the lumpiness in the lawn while the ground was soft. It did a little, but not that much. I ended up tilling up a few sections, then rolling it to smooth it out which workes better. It could be that your roller just doesn't have the weight to get you adequate ground pressure to do what you want to do. It then becomes a cost/time study to see if it's worth building another or buying one.
If I were to get another roller, I found that Tractor supply has some nicer metal ones that were larger diameter, which would have better ground pressure. At the time I bought mine, TSC didn't have them stocked. Also the poly roller gets a flat spot if it sits for awhile. I have mine filled with water, and I won't dump it until fall. It can be filled with sand too, that might help. I think the poly rollers sold by Northern Tools are advertised to be reinforced to prevent flat spotting.