Can you be in ROTC or a officer with tattoos?

I do not understand the younger generation's desire to get tattooed. That having been said, I can see why one would have an emblem or symbol, which has great meaning, tattooed on, like a military unit patch. But, to just cover your arm with a pretty picture -- I don't get it.

Yes you can. I have my shoulders and upper arms covered. I am probably going to get a sleeve soon. It used to be taboo to be an officer with a sleeve. It is more acceptable these days.

Officers go by the same regulations as Enlisted. Look under AR 670-1 for Chapter 3-3 page 12.

Used to be tattoos were taboo for officers. I was amazed at DCC how many medical officers were tatted out

Choose wisely if you get tats as regulations do change. Make sure you are in regs before you get one.

Yes but...regs are changing constantly, if the tat is offensive/ on your face, probably not going to get that waiver.

These days, yes. Nothing on the face, neck or below the sleeves on the hands, although they were allowing ring tattoos for awhile. They can't be racist, obscene or gang/extremist group related. See the current rules for confirmation since they change fairly often.
The Coast Guard was the last service that held out on visible tattoos. My son tried to join the CG back around 2009 and couldn't get in with the leg and sleeve tattoos. The last I looked they are following the same rules as the Navy today.
Even though it was considered taboo in my days, probably the majority of the Infantry Officers in my era had some type of shoulder tattoo. Airborne, Ranger, Death From Above, etc. I just have scars.

If you get tattooed then choose wisely. You also need to accept the consequences of your choice. The wrong symbol, inappropriate language, or a name you may come to regret can impede your selection for assignment. What was okay 10 years ago may not be okay now. Should it make a difference whether you have one or not? It probably should not. However, it may make a difference to the person who is the selecting officiant. That can be positive or negative. No matter what you choose to do or what happens in your career because of your choice, be prepared to own it!

Here's a link to a 2017 Air Force policy.
https://www.af.mil/Portals/1/documents/cct/2017/CCT_011217.pdf?ver=2017-01-12-130729-393
All of the Services have regulations covering this subject. O and E are usually covered under the same policy. Waivers may be available for recruiting purposes.

As long as they meet the regulation, sleeve's are fine. ROTC is a college program so don't base what the Military accepts on what you see in the ROTC program.

As long as it’s in regs. I know a TON of Os with sleeves.