You are not proceeding far enough, the flavours you are experiencing are typical of "lightly roasted" coffee.
Generally speaking, you need to see atleast a nice "cinnamon" colour or your coffee will still have the woody flavours of the raw coffee seeds. These flavours also contain quite a deal of natural acidity. The more or darker you roast the coffee, the more of the acidity and woody flavours are cooked off, the coffee smooths out (loses wood & acidity) and develops complex characters, and the more you proceed after that, the more of a tangy, smokey flavour you pick up as the coffee turns to charcoal, and the more complexity you lose.....generally speaking.
There are a few variables you need to control such as the size of the batch, the strength of the heat, and the distance of the heat source from the beans, and the speed of agitation of the beans while roasting. Playing around with these will produce differing results. Roasting too slowly "cooks" the beans and loses a lot of flavour, and roasting too quickly burns the coffee and or scalds the outside of the beans...
So, the rest is up to you, with further advice from those that have experience in roasting the same way you are doing it.