Is that part of a rollercoaster?

Nope, part of a skylift ride such as this. The lights were mounted on the "scaffolding" of the top pile, where the ride turns around and goes back down the hill. One cable is towards the top of the pic and the other is visible in the bottom left corner. They left the skylift ride up (though removed the seats, so it's just the wires and poles). Not sure if they plan on keeping the skylift ride for nostalgic purposes or eventually getting rid of it. I assume if they were going to get rid of it they would have by now.

I found a picture of this place on google lol. It looks like a creepy abandoned park. (even though it is pretty much)

The pic on the left is of the haunted house ride. That's long gone. I see the M-400 was missing its glass even back then. It isn't a creepy abandoned park anymore. It's a state owned open-land part now (just grass and nature lol).

Rocky Point Park was unfortunately the victim of corruption, which is why it closed down. From what I understand, Rocky Point Park was purchased by a private company. This company owned other assets and used Rocky Point Park to fund those other assets, transferring millions of dollars in "donations" from the Park to their other unrelated assets. Their plan was to bankrupt the park and redevelop it for real estate (condominiums). However, one thing led to another and the park ended up being the center of many court battles, lasting well into to the 2000s, the park remaining vacant since the mid-90s. In 2010 or 2011 the State purchased the waterfront portion of the property and made a public walking path. In 2014 they purchased the whole 114 acres after people of RI approved a multi-million dollar budget to buy the land. So the land will no longer be privately developed and will remain a public State Park.