Should I roll my IRA into my investments and close the IRA?
I really don't want to be pedantic, but some of these terms have particular meanings that could cause us to give you the wrong advice. Most responses here are assuming what you mean by investments is a non-retirement brokerage account, and are giving solid advice for that case. But you also used the term "roll" which is a particular type of transfer from one retirement account to another retirement account.
Also, you can (and should!) have the money inside your IRA invested. An IRA is like a bucket that can hold a bunch of different investments. In fact, nearly any reasonable investment you have access to elsewhere can be held in an IRA.
You should think strategically about your IRA withdrawals. Your IRA is most likely a
traditiona IRA. If so, it's treated like income when you withdrawal it. So it's a bad idea to take it all out at once. It's also a bad idea to use it for a large purchase, like a house. There is a 10% tax penalty if you're under 59 1/2 years old.* If you're over 59 1/2, consider withdrawing only up to the next tax bracket, or only as much as you need to quality for particular insurances. When you take out a little at a time, it doesn't torpedo your taxes by placing you in a higher tax bracket.
*There are some moves where you can avoid the 10% penalty and access it before 59 1/2. It involves converting a
traditiona IRA into a
Roth IRA, and letting it age 5 years. Converting a
traditiona IRA into a
Roth IRA is also a taxable move, so you can use it to increase taxable income.