I don't keep Rosy Boas myself, but I can give some general advice.
According to this caresheet I found on Google, the temperatures in your tank are on the high side:
Temperatures should be between 80 and 85 °F (27 and 29 °C).
On the other hand, this other source says the following:
The hot side basking spot should be at 88-90 °F (31-32 °C). Put one hide there and another on the cooler side. This cool side can be between 75-80 °F (24-27 °C). At night, it can drop down to 72 °F (22 °C) ambient temperature.
So the temperatures in the hot spot might be a bit on the high side. More interesting is the temperature on the colder side of the tank. If this is still too warm to the liking of your snake, they might try to cool themselves down by lying at the far end of tha tank.
Snakes thermoregulate. This means that they move around to a place where the temperature is just right to their liking at that time. That doesn't necessarily have to be the hotspot. So just the fact that they go to the cold side doesn't really worry me.
The second link I posted mentions minimal temperatures of 72 °F (22 °C). If the snake is this temperature, they will feel cold. That is because your hands are much warmer than that. That alone is not something to worry about.
I personally haven't really found a correlation between whether the snake is on the hot or the cold side of the tank and whether they take food or not. So I wouldn't be worried for now and just offer him food as normal.
Snakes in general like to hide and Rosy Boas do that by burrowing. So the fact that they did that is nothing to worry about. Also that they immediately after moving again tried to hide is the same thing, expected behaviour.