The impala ss LT1 did not come from the factory with roller rockers, they came with stamped steel rockers. If you are installing roller rockers in yours, the common advise is to go 1/2 turn after 0 lash, when the pushrod no longer moves up and down.
Wikipedia shows the Toyota AR engine with roller rockers started in 2008. This particular engine has many low friction benefits to it.
It's not really about what rockers you run. If you have guide plates, you need hardened push rods.
No it does not, unless someone put them on it, Not factory on that year.
No it does not. Unless someone else installed them. Was not factory.
yes
Take off one of the valve covers, if the rocker has a roller tip on the side which it touches the valve spring then its a roller, if no roller tip is present then its a normal tappet rocker.
If you have a 2001 or newer engine, it comes with roller lifters and roller rockers from the factory.
yes, with roller rockers.
They can be ordered with 3/8" or 7/16".
Not if you did it right the first time.
1.5:1 with 3/8" trunions.