First time gardener here...

I just planted a veggie garden. This evening I noticed a bunch of ants
crawling on the leaves of all my plants. I'm guessing ants are harmless but
I wanted to check to make sure.

Also, I have about three ant hills in the yard. My dad suggested pouring
gasoline over the hole to kill them, then again he thinks anything can be
taken care of with the right combination of gas, oil and rock salt (no
offense dad!). What can I do to get rid of them which would be
environmentally conscious? Is there a way to get rid of the ant hills
without killing the ants?

On to roses... There's a huge rose bush on the side of the house which is
just starting to bloom. Some of the stems are 8 feet long and obviously
this thing has been let go. Certain stems have leaves which are much bigger
than others with the roses. The question is--how do I trim this? What do I
cut? I feel like a fool for asking, but I don't want to damage the plant.

Thanks in advance.