I just this last year rolled my 401k into a traditional IRA. I called Ameritrade the brokerage I rolled it into. They will not issue supporting tax form until may.

Ask the brokerage you rolled it FROM, not the one you rolled it TO, when/if they will issue a 1099-R.

You don't need the form 5498 they are sending in May.  You just enter the 1099R you got from the 401K.  What code is in box 7 on it?  It may ask what you did with it and you pick I moved it to another retirement account.  Read the questions slowly and closely.  If you don't under stand one post back.

You can just type 1099R into the search box at the top of your return, then find and it will give you a Jump To link to go right to it.

OR Enter a 1099R under
 Federal on left
Wages & Income at top
 Then scroll way down to Retirement Plans and Social Security,
Then IRA, 401(k), Pension Plans (1099R) - click Start or Update

If you get the screen of partners you can import from click the bottom circle for I'll type it in myself - Continue
The next screen should be What Type of 1099R is this?  With 4 choices.  Pick the right kind you have.
And on the same screen you pick which person it is for if you are married.

By "this year" if you mean 2019, you won't get anything from the brokerage on it for tax purposes until you file your 2019 return "next" year. You have nothing to report concerning this on your 2018 return.

I rolled it in June of 2018

You need a the 1099-R from the 401(k) plan administrator.  The 5498 that Ameriitrade will send is information only.

I received the 1099R from the 401K administrator.  The 5498 I will not get until May 2019

You don't need the 5498 for a rollover like this.

Like I said, the 5498 is only information to you.   It does not go on a tax return.   Just enter the 1099-R.