If I have entered gas royalty income as 1099-MISC income, should I enter it again as royalty income?

If you have already input your Form 1099-MISC information once into TurboTax for your royalty income, then you should not have to do it again, separately, through the Rents & Royalty section of the TurboTax data entry.

That said, there are at least a couple of different ways that you can verify that your royalty income is properly reflected (just once) on your Form 1040 Schedule E (where royalty income belongs).

First, if you are using a desktop version of TurboTax, you can preview your Schedule E itself by finding it among the list of tax forms, schedules, and worksheets, by accessing the Forms Mode of the program (here is a link on how to do that):

https://ttlc.intuit.com/questions/1914350-how-do-i-switch-to-forms-mode-in-the-turbotax-for-windows-software

Second, you can preview your main tax return, Form 1040 itself, and see if there is a figure reflected on Line 17 (rents and royalty income).  If you have multiple rent and royalty properties that could appear on Line 17, then does the Line 17 figure change at all when you add (or subtract) your 1099-MISC data?  That would be the relevant question to ask.

As to viewing the Form 1040, in desktop TurboTax this is easy to do by simply accessing the Forms Mode of the program and selecting your 1040.  In TurboTax online, there is also a procedure for previewing your 1040 (but not Schedule E), which is detailed at the following link:

https://ttlc.intuit.com/questions/1901539-how-do-i-preview-my-turbotax-online-return-before-filing

Third, you can contact us for live support.  One of our tax agents can screen-share with you, and / or, using one of above methods (as well as some other ways not detailed here), can quickly verify if you have your royalty income, from the 1099-MISC, accurately included on your tax return.

We are live during the busy tax season from 5AM to 9PM (Pacific Time), 7 days a week.  During the rest of the year, we are open Monday - Friday, with normal business hours.  Here is the link to our main support ticket webpage:

https://support.turbotax.intuit.com/contact/