Adjusting the right dose of elements in the game is probably the hardest job for a DM. You kind of have to hold the player's pulse, see when and where their interest is peaked and when they have that sparkle in their eyes. As a DM, you may want to run a certain kind of game, but it's ultimately up to the players whether to accept and enjoy your methods, or... well... be bored with them.
I find comedy is a good way to lure a combat interested group into a bit of the roleplaying aspects. It might start as a frantic goblin surrendering to the PC's and weaving impossible stories. Some classics like damsels in distress, and stuff that can be easily identified from iconic movies, books, or stories usually also draw some attention. You can describe a race chariot as the millenium falcon of chariots with bits and bobs sticking out from everywhere, and it'll take an A-team effort to get it in top racing condition again. Finding what the players like, and playing to those likes with analogies can go a long way into increasing the entertainment value of non-combat encounters.
As for general railroading, some parties are very indecisive, and when presented a half dozen options, they are more likely to sit and debate and do nothing, so as DM, you have to come up with ways to prod them in one direction or another (i.e. railroad). But there are tricks you can use to make them think they made the decision. Have a couple people make knowledge checks like history or nature, to point something out to them, have someone make an insight check to help them out with understanding enemy motives.
At times the indecision can come from a lack of information, and it's difficult to see this as DM (because you know everything). Just give them stuff they can identify with. You want them to go looking for a missing dwarf, have another dwarf drop the missing dwarf's clan name, which perhaps happens to be of the same clan as a PC. It's still railroading, but you are at least giving the players something a little more to care about, than enter room 113, kill monster, loot treasure, rinse, repeat.
If your getting bored due to running a series of combat encounters is the main problem, I find that a goal other than "kill 'em all" will keep me interested for longer as DM. And it's not easy to come up with such scenarios all the time, so I like the challenge. I introduce some new mechanic in encounters depending on my goals. In a recent boss fight, I had a magical nexus in the area that the PC's and the boss could draw energy from, using skills (arcana, religion, nature, etc), for various enhancements (damage bonuses, temp hit points, resistances, etc.) The boss was summoning dretches out of the nexus. Anyway, whatever the mechanic, I find it enjoyable to bring something new to the table with terrain mechanics or monster mechanics even in a combat heavy game, and create goals other than total enemy annihilation.