Safety and tranquility are both important aspects of investing for retirement. Yes, we want stocks with meaningful upside. We also -- however -- want to own companies that we are confident can continue succeeding for the very long term.

It's these dependable companies that allow us to get a good night's sleep while owning shares, and it's these companies that work well for reliably building retirement wealth. Here, we explore two rock-solid stocks that can do just that.

1. ViacomCBS's transformation 

Man and woman hugging and smiling

Image source: Getty Images.

While revenues for ViacomCBS (NASDAQ:VIAC) (NASDAQ:VIAB) are still hampered by the pandemic -- down 9% year over year -- the trends are improving and the company is delivering elsewhere. In its most recent quarter, its reported free cash flow more than tripled year over year to roughly $1.5 billion. With an enterprise value (EV) of around $52 billion, this level of cash generation is quite notable to say the least.

Furthermore, through non-core-asset sales -- like its publishing house -- the company is raising even more cash to pay down debt and to de-lever its balance sheet further. While its leverage ratio is roughly 3.4 times today, ViacomCBS remains committed to bringing that down to 2.75 times eventually -- paying down debt should lead to direct multiple expansion for the company. Finally, the organization pays out a nearly 2% dividend annually.

Profit generation and balance sheet health are nice, but we still want growth, and this stock is starting to deliver it.

ViacomCBS has traditionally been known as a cable entertainment conglomerate, but that is no longer the case. The company has committed to building out its own free and paid streaming services in response to the world's cord-cutting revolution.

On the free side of things, ViacomCBS's PlutoTV service is finding meaningful success. Its domestic monthly active users grew 57% to 28.4 million and its advertising revenue more than doubled -- both year over year. To bolster the service's reach, it signed distribution deals with LG and Sony and launched in Spain and Brazil. Pluto is expected to debut in France and Italy this year.

Its paid services are also excelling. Subscribers between SHOWTIME and CBS All Access spiked 72% year over year last quarter to 17.9 million. The outperformance prompted CEO Bob Bakish to raise his year-end subscriber forecast for the second consecutive quarter to 19 million.

This growth is all before CBS All Access's relaunch as Paramount+ on March 4. ViacomCBS will be integrating far more scripted content, as well as a plethora of its live sports broadcasting rights, to sweeten the value proposition further. Champions League, the National Football League (NFL), and much more will be available on the new service -- this should really help with subscriber growth, considering that 88% of television's most popular shows are live sporting events.

2. Facebook looks unstoppable

Despite all of the advertising drama Facebook (NASDAQ:FB) has dealt with over the years, it's still thriving. In the company's most recent quarter, sales grew 33% to $28.07 billion. Its operating margin and cash flow from operations margin both expanded briskly, and its earnings per share spiked 51% to $3.88 -- beating expectations by 19.7%.

The company even added $25 billion to its existing $34 billion share repurchase program. Based on this, its forward price-to-earnings ratio of 25.7 seems very modest.

Even on such a large base of roughly a third of the planet, Facebook delivered 12% MAU growth to 2.8 billion people year over year. Incredibly, it now attracts nearly half of the planet to its family of apps on a monthly basis (3.3 billion people).

To further capitalize on its massive user base, the company has been rolling out shopping features to its Facebook and Instagram apps. Based on a compounded annual growth rate of 14.7% expected for global e-commerce through 2027, this seems like a good move. Facebook's average revenue per user (ARPU) growing at a brisk 19% year-over-year clip provides some evidence that this endeavor is beginning to work.

If that wasn't enough, the company's recently released virtual reality gaming product -- Oculus 2 -- is a hit; vendors are having trouble keeping it in stock.  Its "other revenue" category -- which includes Oculus 2 -- soaring 147% year over year is simply an effect of the Oculus cause.

Two stocks to invest in

ViacomCBS and Facebook are companies capable of generating retirement wealth in a responsible manner. Each has assets capable of realizing growth with more established businesses already creating significant free cash. Both stocks are in my portfolio, and I strongly believe you can feel comfortable owning the two for retirement as well.