Higher risk = high reward?

Some theory (in my understanding) suggests that price is the expectation of future cash flows discounted by expected return: $$p_t=\frac{\mathbb{E}^m_t[c_{t+1}+p_{t+1}]}{1+\mathbb{E}_t^m[r_t]}$$ where $$c_{t+1}$$ is the cash flow at time $$t+1$$, $$p_{t+1}$$ is the resale price at time $$t+1$$, and $$r_t$$ is the realized return of period $$t$$, known only at time $$t+1$$. Here the expectation is taken under a measure that represents the market aggregate belief, which takes into account all public information at time $$t$$. The efficient market hypothesis suggests that this belief indeed is the statistically correct distribution of the real world, so $$p_t=\frac{\mathbb{E}[c_{t+1}+p_{t+1}]}{1+\mathbb{E}[r_t]}$$ where the expectation is taken under the actual probability distribution that characterizes the real world dynamics.
Here is my question: if what's said above is true, then does it mean if I find a bunch of investments with high risk (so discounted more heavily) that are uncorrelated with each other, then I can achieve a higher expected return of the portfolio in a diversified way? Some of the expressions above might be imprecise (so is my understanding) and I would love to be corrected.