David, the rate of return you can project for retirement accounts is directly related to how much risk you take in the account.   Over the long run (decades) stocks have averaged 10%-12% while bonds have averaged approximately 5%.   Cash has averaged slightly less than bonds.   For a very conservative investment mix (all cash and government bonds) you might use an assumed rate of return of 4%.   Mix in some stocks and bonds (approximately 60% stocks and 40% bonds and cash) and you might be able to project 7%-7.5%.   However, different time periods can radically affect returns, as we have seen in this decade.   The longer the time frame, the more chance your numbers will be met.   I’m not sure how old you are, but for someone in their twenties or thirties, a mix of stocks, bonds and cash should allow for a projected return of 7% over the long run.

As I'm sure you do, I like the 4% interest in today's environment.   However, the Roth-IRA option is very attractive as a retirement savings vehicle.   Your age plays a role in my answer as well as how long you have held the bonds. Any help with those two issues?

I have not worked directly with reverse mortgages but from what I have seen, the fees are something that you need to make sure you understand.   It appears that pretty significant expenses can be built into the process.   You would also want to check for the most competitive interest rate and be sure to understand what happens at death.   However, the house, as an asset, should be used to make your grandmother's life as pleasant as possible for as long as she needs it.  

The Roth-IRA is a personal savings account, the Roth 401(k) is an employer based account.   They are similar in how they both allow after tax contributions to grow tax deferred and for untaxed money to be withdrawn and spent income tax free if certain conditions are met.   However, there are some significant differences.