I am trying to make dill rolls and I am following the recipe but cut it in half. Instead of margarine I used butter and vegetable oil. Those were the only changes I made. I also used the kitchen aide dough mixer and mixed it for about 3-5 minutes. I let it rise and it doubled in size, but for the second rise my dough went flat. It never rises again. It also would not brown and did not taste good at all. What am I doing wrong? I'm at normal altitude. I have included the link for the website.
I can't say what you did wrong or if it was the yeast at fault as suggested as we can only go by your results. I'm not so sure the yeast would be faulty though since you said it doubled in the first rising.
They look like they 'sort of' rose but more sideways since they're melded against one another. Or did you put them touching each other to begin with? The baked buns in the link have a wide spaces between them so if you spaced them that way, the did rise but not properly.
If you left spaces between them and they spread out when rising but didn't hold their shape, how soft was your dough? Softer dough with higher hydration don't rise high and keep their shape as well as lower hydration doughs.
If that doesn't fit your dough, is it possible that the temperature used in your first rising was too warm? A couple of times when I was trying to hurry the process (even though I know better), I've subjected the dough to too much heat. It rose quickly and doubled in bulk but most of the yeast was killed. The second rising didn't go well with most of the yeast dead. Is it possible you did something similar?
Sorry to ask questions instead of giving a concrete answer but all we can do, from our end, is guess and hope something fits. Looking carefully at your photo, there are air pockets like bread should have but with a mix of small and big spaces like dough with high hydration has. The surface of the buns are uneven too. When you shaped the buns for the second rising, we're they rounded and smooth like the unbaked buns in the link?
Hopefully if you provide more information, others may see other possible reasons.
It is hard to say based on your minimal description. Please give a detailed step by step description of your process.
Kitchenaid mixers are great all around machines but they are not great at bread mixing. I always finish my dough's by hand on the counter to avoid long mixing times overheating the dough. 3 to 5 minutes in a kitchenaid is not enough to get proper gluten development in my experience. Once you have finished kneading the dough on the counter you then need to place the dough in a lightly oiled bowl for the the "first rise", you want it rise but not to much as you can exhaust the yeast ( it appears to me that you have a dough that was not fully developed AND you let it go to far on your "first rise".)
You let it rise in the bowl close to but not until doubled, you want to be able to poke your finger into the dough and have it spring back some but not to much or to fast and if it seams to collapse and not spring then it has gone to far. You then fold the dough ( punch down ) and turn it and let it rise to the same point again.
Now you are ready to turn it out onto your bench (counter) and weight it ( divide it) into the loaves or roll sizes you need, cover it and let relax for about ten minutes and then form into loaves. You let it rise until it is ready to bake, again you use the finger test as you do not want to let it go to far. This is a slightly different feel then your first rise. testing the dough's spring is an acquired skill and you will get a feel for it ( pun intended ) the more you bake. I was baking bread as i wrote this, here is a photo.