You phrase this choice as a simple binary ("managed portfolios vs. Roth IRA"), but there are really two dimensions to the question here.
1) What do you want to invest in?
2) What type of tax shelter, if any, would be the best place for that investment?
A Roth IRA isn't an investment, it's merely a special tax-sheltered bucket of money that you can use to invest in whatever you want. You can buy stocks in a Roth IRA, you can buy bonds, you can hold cash, you can even buy a rental property. In fact, the FAQ section on
Ally's Managed Portfolios advertisement page mentions that they'll be happy to do their magic in a Roth IRA. It's therefore not a choice between a Roth IRA and this Ally investment service at all; you can easily do both if you wish.
Looking at the first question, what to invest in, this Managed Portfolio service is an okay option. My biggest criticism would be the mandatory 30% cash cushion. For one thing, this is a really big fraction of your wealth to have sitting around losing value to inflation every year. For another thing, you don't really even get to take advantage of the main reason many folks like to have a cash cushion in the first place: to have the opportunity to withdraw exclusively from that cash during a market downturn so that you don't need to sell any other investments at a low point. Instead with this account each and every withdrawal will be 30% cash and 70% other investments whether you like it or not.
A lot of folks on this forum will recommend that you pick a more DIY solution like some variation of the
three-fund portfolio. This adds a bit of complexity, but you get a lot more control. Someone just learning about this stuff like you might prefer to start with an all-in-one solution like a
Vanguard target date fund.
As to the second question, where to put your investments, a retirement account such as an IRA is often a great choice. Again, you can have your Ally Managed Portfolio in a Roth IRA if that's what you really want to do. I encourage you to read a bit more about investing, such as the JL Collins stock series mentioned above, before you make too many decisions. There isn't a huge hurry here. Take a month or two and educate yourself.
