Quarterly earnings don't often change a company's investment thesis, but sometimes they are enough to convince some investors of what others already saw. Recently, Teladoc Health (TDOC 1.95%) and Roku (ROKU 2.55%) reported second-quarter results that sent their shares soaring, but in both cases, there were solid arguments for buying the stocks before these latest updates.

In fact, these arguments remain intact for both Teladoc and Roku. Let's find out why these companies are worth investing in today.

1. Teladoc Health

Like other telemedicine specialists, Teladoc saw its shares soar along with its financial results in the early days of the pandemic. Patients switched to telehealth for medical needs, such as basic prescriptions, consultations, and referrals. But Teladoc's business started slowing once things were getting back to normal. That, added to the massive net losses it incurred last year, sent Teladoc's shares down the drain.

The company is bouncing back, though, as its second-quarter results suggest. On the top line, Teladoc reported revenue of $652.4 million, an increase of 10% year over year. That's not where most of the progress happened. Teladoc reported adjusted earnings before interest, taxes, depreciation, and amortization (EBITDA) of $72.2 million, 54% higher than the prior-year quarter. The company's net loss per share of $0.40 was substantially better than the $19.22 loss per share reported in Q2 2022.

Further, Teladoc continues to register excellent gross margins, which rose by 1.6% year over year in the second quarter to 70.8%. No wonder that Teladoc's shares jumped on the news, but short-term gains aside, there remain excellent reasons to be optimistic about the company's future. For one, Teladoc is still growing its ecosystem. The company's mental health unit, BetterHelp, continues growing fastest. It ended the second quarter with 476,000 members, an increase of 17% year over year.

Second, the telemedicine industry is just getting started. According to some projections, it will register a compound annual growth rate of 24% through 2030. That makes sense. Telemedicine is convenient and confers cost and time savings to patients. One study estimated that it saves between $19 and $121 per visit. Third, Teladoc's high margins should lead to profits eventually once it becomes a more established and recognizable company and its customer acquisition costs decrease.

The company's latest results were solid, but investors should stick around well beyond the jump it experienced following its second-quarter update. 

2. Roku 

Streaming giant Roku has faced major issues over the past couple of years. First, its expenses rose due to inflation and supply chain issues. And instead of passing these higher costs on to its customers by increasing the prices of its namesake streaming devices, Roku decided to absorb them. Second, Roku's revenue suffered as advertisers decreased their budgets.

These two issues explain why Roku's stock performance has been unimpressive over the past year, but the company's second-quarter results showed progress. Roku reported revenue of $847.2 million, an increase of 11% year over year. That's a much better growth rate than Roku had registered over the past two previous quarters. Roku's net loss per share of $1.02 was much better than the $2.04 recorded in the comparable period of the previous fiscal year.

With a rebound in the advertising market, Roku's revenue growth should continue to pick up. Elsewhere, it is still increasing on key metrics, such as active accounts and hours viewed. The former saw a 16% year-over-year jump to 73.5 million in the period, while Roku's hours viewed came in at 25.1 billion, 21% higher than the year-ago period. This is important, as the more the company attracts viewers onto its platform -- and the longer they stay glued to their screens -- the more advertisers will follow them wherever they can find them.

According to the research company Nielsen, the Roku channel accounted for 1.1% of television viewing time in May. The entire streaming industry grabbed 36.4% of viewing time, showing massive room for growth. That's what Roku's future hinges on. As streaming continues to become the norm and absorb more and more viewing time, Roku will be a winner, no matter whether it is Netflix, Apple TV+, or Amazon Prime Video that rises to the top.

And given the vast worldwide opportunity, Roku is in it for the long haul. Investors looking for buy-and-forget stocks need look no further.