So I recently learned that I have about $2,000 in an individual IRA from a job that I was at for about a year. This was during a time that I gave zero shits about retirement and finances in general other than "do I have enough to pay my bills, eat, and buy dumb shit?" Which is why I forgot all about it. After learning that my parents are going to retire with almost nothing some years ago, I got my ass in gear with learning to budget, getting a higher paying job, and aiming to max retirement investments. I learned about this account because they recently transferred the funds to a different company to manage it so I got a notice in the mail.

Long story short, I want to transfer that into my employer TSP 401k account (traditional TSP, not Roth) just so I have everything in one place as far as management and adding a couple of extra investment drops to the current bucket. I do also have a Fidelity Roth IRA, but not a traditional through them. I called the TSP number where they handle the transfer for you, but the chick on the other line seemed so annoyed that I didn't know all the jargon she was talking about that I just gave up. I was going to call again, but I was on hold for 45 minutes last time so that kind of took the wind out of my sails at the moment. She kept saying to make sure "Your account is in cash or you'll get a giant penalty."

Currently that account with $2k in it is 100% invested in FXAIX, like my Roth account through Fidelity.

My understanding is that if I'm transferring 100% of the funds from a traditional IRA to a traditional IRA that there are no penalties. I just need to make sure I'm under the yearly contribution max, which sadly I still am. But I'm getting there.

Anyone every done this that could offer any insight? I tried watching some Youtube videos and hitting the DuckDuckGo engine but nothing I found solidified anything where I was confident that I was doing the right thing.

I've got a pretty decent TSP balance and I would not put those funds into your TSP.

Put them into your Fidelity account for more options, both now and (especially) in the future when you retire.  Customer service, as you've seen, will probably be better too.

I'm grateful for the TSP so this isn't a knock on them.... it's just the way things be.

Yeah, I may just go that route. I was impressed that I got a call from a actual person thanking me and wanting to know my goals when I opened that Fidelity account with a measly $100. Given it's only $2k would it be better to just take the tax hit on rolling it into the Roth?

I don't think anyone but you can answer that... don't know your age, income, other investments, etc., but if you're going for simplicity (which it sounds like) then probably so.

All I have is TSP and taxable mutual funds, so I'm not an expert / advisor by any means.

The account that this $2k is in isn't Fidelity. It's some place called Integrity IRA. They offer like 5 index funds and that's it (one being FXAIX). I thought it was a scam site at first, lol. If it were in Fidelity already I probably wouldn't bother. I still might not bother. I'm in my mid-thirties and make a little over 100k a year, household income a little over 200k. Looking at some calculators it seems like it'll cost me $500+ to convert to my Fidelity Roth. That stings enough that I may not mess with it even though I realize it's a fairly insignificant amount of money in the big picture.

Tsp has very limited options.  Fees are low though.  
I would open a rollover ira at fidelity since your roth is there.  You can do it online with a few clicks and then just provide the mailing address or routing info for your rollover and you’re done.  A rollover ira at fidelity will let you invest the money in anything you want rather than the few options tsp has.